What is your GM Style for reacting to player's roll, do you let your players narrate what happens from that roll (Within reason) or do you narrate what happens for them how they react or do you try to do a mixture of these two styles? Personally, I try leave up to the players as much as possible but will take over when need or to narrate a certain result (specifically for despair results).

I may make suggestions, but I generally let them narrate it. With Threat, I will often be somewhat specific about what happens. I will often narrate the opposition's response to the active character's actions.

try and let them narrate the results of their roll. this takes some of the work off you. Also have the players narrate their opponents threats and despairs. have suggestions for triumphs for all of their triumphs so if they dont have an idea you can make suggestions. Really everyone should work together it flows much better.

For me, it usually depends on how experienced the players are, and also what kind of game I'm running.

When it comes to combat, I generally let the players dictate the narrative if they want to. Newer players will generally contribute less to the narrative, so I'll happily give them suggestions or just dictate some good or bad things that can occur given the circumstances. I have one guy who does a lot of LARP and is much more comfortable with then RP aspects, so he'll quite freely make up narrative (even bad stuff that happens to his character on threat or despair, because he loves the drama and understands that half the fun is getting out of trouble once you're in it). As a result, they make inventive things happen in combat and its more fun for everyone.

For non-combat situations, they usually enter with the objective of controlling the narrative as much as possible, rather than just trying to not die. As a result, I do quite a lot of prep on non-combat encounters (negotiations, social disagreements, making shady deals, mentoring followers, etc.) so they usually let me throw them suggestions so they can pick up the clues. Usually in those situations they'll use the Triumph or Advantage to ask pointed questions so I can give them narrative that matches the degree of their dice results.

e.g. Negotiation with someone selling a ship. They roll a failure with two advantage against the seller in the negotiation. "He's not moving on the price, and looks a little impatient like you're wasting his time." Player asks "How do his crew look? Are they angry too?" I tell him "No, not angry. But one of them looks nervous, as though he would rather get this over with."

In the scenario, they're talking to a bunch of pirates who have stolen this ship only to find that it was owned by slavers. The pirates are trying to flog it before anyone traces it back to them because slavers don't play nice. The more narrative success they get on the dice, the more clues they pick up that something's wrong. They can use it to their advantage to get a lower price.

Kinda long answer, but I hope it helps.