If there is a set number of people, let's say 3 for example, then the easiest option is probably to have a parallel gateway that runs to 3 user tasks, each one assigning specifically to that employee by username.  This is a big benefit because they can all do their part simultaneously, but it's limited in the way that it is hardcoded to the specific number of users.

If you have a maximum number of assignments, but it could be smaller, you could do the same thing, but using an inclusive gateway instead of parallel.

If the number of users you need to respond are variable, then it gets more complicated...

A couple ways you could handle something like that:

In a prior form do a database look-up from the tables in the LFForms databse to populate a table with the users in a particular role in a particular team (this may be helped along by setting up a View on the LFForms database to display the data in the manner you need rather than trying to set-up search criteria within Forms).  Then have each user comment in that table next to their record, perhaps with some Field rules to hide the rows of the table that don't belong to them.  Then your process checks if all of the comments in the table are complete, if they are not, it keeps reassigning back to the team.  You could even set-up filters to only get the users in the table who are not yet complete.  This is complex, but doable.

You could do something similar to that last one, but do it via Workflow.  Have the workflow determine the list of users who are incomplete, and populate a field on the form with the name of the first one.  Then have the form just assign to that first one.  After each submission, it triggers the workflow again, and the next name is populated.  Only after all names are exhausted (maybe the field now populates blank from Workflow) does Forms let it proceed to the next stage.  The downside with this is it's going sequentially, so everyone is waiting for the person before them.

You could build your filter to identify all of the prior users who have submitted the form, and exclude them from the team being assigned.  After the form is submitted, it goes to a gateway to determine (somehow) if all the required actions are complete.  If not, it goes back to the user task, reassigning to the increasingly smaller team filter.  Otherwise, it continues on to the next stage of the process.