Well, if you've can afford this rollback to take as much space as it needs (or as much as there is available in its tablespace), then why not set MAXEXTENTS to UNLIMITED? You can allways shrink it back when the transaction is finnished and reset its maxextents to whatever you want. BTW, what are the INITIAL and NEXT settings for this rollback segment?

Anyway, can you tell us how many records (out of how many in total) are you deleting with this transaction? Perhaps it would be faster (and less RBS space demanding) to insert those records that are not to be deleted into an interim table, truncate your table BLAH and reinsert the remaining records from the interim table.

Also, indexes can contribute extensively to the required rollback space needed. If you can afford, it might help if you drop (at least some of) the indexes on your table and recreate them after the delete is done.