there are 2 ways (if im not wrong) to this method...
one u have ur hand as a pivot point or the rims as a pivot point...
Tim waterson demonstrates the push and pull method with ur hand as a pivot but i don't have that video so i'd just go for the rim method...
basically u just hold ur stick with ur index and thumb. About 1/4 way from the end of the stick, place ur sticks to the rim and using the rim as a pivot, bring it up and down and u get ur motion right, ur rolls will be clean and fast... It's all about practise.. i got mine rolling after at least 3 to 4 days of practising...
great for death metal drumming...