bbPress.org

go to

Dashboard>user>all users

under

Users Add new

you’ll see the worpdress and bbpress roles listed in a single line

eg
All (1,201) | Administrator (2) | Editor (4) | Subscriber (1,050) | Keymaster (2) | Blocked (1) | Moderator (4) | Participant (1,181) | visitor (13)

Click on the ‘blocked’ link and you’ll get a filter which just shows these