"Could not find table 'Role'" - rolify, devise, cancan and a silly mistake

I followed the tutorial on github on getting rolify up and running, but everytime I ran into the problem, that the table "Role" was not set up.
I ran all migrations, even twice, but nothing.

After about three quarters of an hour I found the solution on the issue tracker on github: the "rb" was missing from the migration file!

Putting the RB behind the file and everything worked fine.