A swimlane either accepts user or roles. Users are 1-1, roles-users are mapped in the jbpm tables
Regarding the other question: no, sorry
In our case (we needed to assing some user from Role, defined in project for specified swimlane) we imlemented assignment Handler for swimlanes (added them automatically during process deployment).
This handler is called then swimlane instance in process created (then swimlane used for forst time). In this handler you can assign some actorId to the swimlane - depending from some of logic (implemented by you).
For example - in this handler you may get list of users in jBoss, make decision what user should be used in this process for specified swimlane, and put him into actorId