No, there is no problem with reusing the same rollback segment name when dropping and recreating a rollback segment. Internally, Oracle does everything using the undo segment number instead of the name.

Interestingly, Oracle reuses undo segment numbers too. When you drop a rollback segment, its row is not deleted from UNDO$. The STATUS$ column is just changed to 1 and the wrap number and sequence number are retained. When you then create another rollback segment (using the same or any other name) it will get the same undo segment number and the wrap and sequence numbers will start where the equivalent number for the previous rollback segment of the same number stopped (unless the wrap number was already too high to permit more transactions). This of course necessary so that old row level locks once held by transactions assigned to the previous rollback segment of that number can successfully be cleaned out.

I was told by my Oracle Perf Tuning class guru that any new RBS must not have the same name as a previous one. His reasoning was that it could cause problems with recovery, should it be needed.