Managing multiple processes

I´m currently using Bonita bpm in my company for one specific process; as we are having good results with it we want to implement new processes but I´m not sure how several process are handle in Bonita; for example, if we have 50 users working in the current process and these group of users will be part of the new processes too, how do you manage roles, user names and passwords? do you need a new one for each processs? how will the tasking screen look like? how could users move from one process to another and being clear in which process they are working on?

If anyone had has a similar experience, I would appreciate your help.

Thanks in advance