There are two kinds of scenes in 7th Sea: Dramatic Scenes and Action Scenes.  

• Action Scenes are quick-fire things where alot of things are happening in succession: you roll once every round for these.  The scene ends when the action ends.
• Dramatic Scenes are more leisurely and cover a longer period of time: you roll once for the entire scene for these.  The scene ends when people run out of things to do.

Your example, of a fight with a group of ne'er-do-wells, is an action scene.  Keep doing rounds of combat until one side or the other is no longer fighting.

If, instead, the heroes rode into town and the locals all looked at them shiftily and started to whisper behind their hands, you might want to start a Dramatic Scene, where the heroes try to find out what's going on.  They pick their approach and spend their raises to investigate, and the investigation ends when they run out of ideas (raises).

Does that help?

Ok, there is no turn, no round nor an initiative. In a fight like you describe, players declare what they roughly plan to do (the approach) get assigned dice to roll and roll them establishing a number of raises to spend. That number of raises acts as their initiative AND is the number of actions they can potentially take. In an action sequence (like your fight) the scene can potentially end when everyone is out of raises. At that point, the GM has to decide if the scene needs another roll or things have hit a logical conclusion. (And, yes, the GM can decide the heroes have enough advantage to end a fight before the villain is physically beaten down if the outcome is obvious. You can narrate that they "wipe the floor" with the rest of the brutes and move along) If the scene is still in question, you can have players declare new approaches and repeat the cycle. Now in chases and social scenes, (dramatic sequence) the players declare approach, roll dice and have actions to spend until the GM decides the scene ends or changes to the point of needing new rolls. If they run out...too bad for them. The trick for the GM is to pace these scenes where the player may run out if they don't take a few consequences. For length and pacing I recommend watching episodes of Leverage. Particularly episodes where they are pulling robberies. The show will cut between 5 characters in separate locations each with their own goals and risks. Every so often one of them gets hung up and needs help from a teammate (as if they ran out of raises) but you can see obvious spots where the scene would end and shift focus to a new scene. That show has near perfect RPG pacing. Now sometimes there is more to be done in a location than a single Dramatic Sequence could handle. So break it down for the players. First scene handles up until a certain plot point happens. At that point players should have new info to work with and a developed story and you can roll new sets of raises. Now, each roll is an approach and each one can have a different set of stats to use. So don't expect players to lock in on one approach for a fight and stand by it in a series of sequence rolls.

Some good explanations here already, but I'll share how I visualize the rolling mechanics, in case it helps.

Essentially, dice come out in three cases, if you undertake a Risk, if you get involved in a Action Sequence, or if you're participating in a Dramatic Sequence. They're all similar, but have a few distionctions.

Typically, you should only have one type of roll (if any at all) in a Scene.

Risks

When you aren't acting in either type of Sequence, and a Hero wants to accomplish something that might have Consequences (per their Approach), then you would initiate a Risk. These are similar to skill checks in other systems. A Scene can have multiple Risks - for example, you could chain further Risks off of complications from the first Risk - but they do not occur in Rounds or Turns. The player describes the Approach, the GM sets the Consequences and Opportunities along with what needs to be rolled, the player rolls and builds Raises, then picks what the want from the options available to spend raises on (succeeding at Approach, negating Consequences, or taking advantage of Opportunities). If there is a follow-up Risk, then it would be completely separate from the first - getting its own Approach, maybe using a different Skill, and so on.

Action Sequences

An Action Sequence breaks out whenever you have a Scene with high-energy or fast-paced events taking place. The Sequence typically fills up the whole Scene. Action Sequences cover things like typical combat encounters in other games, as well as anything that physically demanding or has a lot going on (this can include things like chases, if you'd like).

Action Sequences are the only time the game is officially broken down into Rounds. At the start of each Round, every Hero and Villain gets to set an Approach, so you you can think of a Round as the few minutes in an action scene in a film where the characters are pursuing one particular goal. After reaching (or failing to reach) that goal, everyone picks something new to focus on. For example, Round 1 could be about finding the Gold Compass Macguffin for your Hero, but in Round 2, you've got the Compass, so your focus is on escape (or chasing the enemies away).

Basically, every Round in an Action Sequence is like a normal Risk, but all the participants take turns spending Raises, rather than just assigning them. Also, they can all share Consequences and Opportunities (you all have to worry about the ship being on fire, or you all have a chance to reel in the Count who has gone overboard).

Dramatic Sequences

When you have a Scene (or a group of Scenes) where a lot is happening that the players are directly acting in, but is more about rising tension, you start a Dramatic Sequence. I think of these as montages in films; there's a lot going on, and either a building sense of success or tension. The book examples of socializing at a ball or infiltrating an enemy stronghold are good, as is following up with contacts. Basically, if you could follow a single character for a few minutes or break down a series of actions into a few quick shots, and set the whole thing to music (and optionally sound effects), it should be a Dramatic Sequence in my interpretation.

Dramatic Sequences are similiar to Action Sequences, with a few exceptions:

• They can cover multiple Scenes. The Hero can move from localle to localle, or you can have different players participating that are physically in entirelly different locations.
• They do not have Rounds. Everyone gets one Approach and one roll. When you're out of Raises, you can't change the narrative of the Sequence (but you aren't necessarily done with it yet).
• Raises are typically spent to influence the story being told. If you're sneaking and guards are approaching, a Raise gets you out of sight. If you're socializing and want to get the other courtiers to share information on one tpoic, a Raise gets them talking.
• Once everyone is done spending Raises, it doesn't mean that the Sequence is over. If you've infiltrated to the heart of the enemy base and you're out of Raises, that could be very bad. Generally, though, it would make sense for GMs to give the player a soft out of the situation, if they want to be fair. "You haven't found the evidence but you can hear the guards being roused. You can cut your losses and get away now, or stay and take your chances, but without any Raises, you'll be at their mercy."

TL;DR

If you're in a fight, that's an Action Sequence. You set an Approach every Round and roll once/round.

If you're doing a lot of the same thing in a row (like sneaking or talking), that's a Dramatic Sequence. You set an Approach and roll once. The Sequence is over after the Raises are all spent.

If you're just doing something outside of a Sequence, that's a Risk. You set one Approach and roll for it, spending Raises all at once. You don't need to roll again unless there's another Risk later.