I roll mine from the top.
I use a drain pipe with a slot cut in it to poke the top into so that the sail rolls up snugly. I remove the battens before rolling because I use the one set for two different sails. I have also been advised that it is best to remove the battens to avoid them becoming stuck in the pockets and to keep the tensioners in good shape.
I use a piece of guttering downpipe purchased from B&Q or Homebase (in the UK). Unsire of the diameter but I would guess around 4". When you roll dont roll too tightly either and if the sail is going to be stored for a while then take it out every now and then and reverse the direction of the rolloing.
speaking of sails. i am about to buy a new standard sail but cant make up my mind between hyde or north sails. hyde is more expensive. but other than that i dont know which one is better. anyone have any suggestions??
They come in 3m lengths, I just bought one of those, rolled the sail how I wanted it and marked the tube leaving an overlap of a few inches at each end and then cut the tube down.
The only issue I found was that some long sail bags come with a rubberised inner coating (notably the Rooster one) which makes it a right pain to get the sail in (I turned mine inside out). The standard blue Laser long bags are ok though.