Using no rudder with them is just developing bad habbits that you will need to break down the road.

Try them at a slower speed, or one or 2 rolls per circle.. need rudder than. Also if you plan on doing rolling harriers that look good you need rudder as well. You can always tell when someone isnt using the rudder in a rolling harrier.. the tail doesnt roll axial.. more of a barrel roll.

The thing with rollers is that they generally take a lot of practice and then one day it just clicks.. its just a rythem you need to find.

To do a proper rolling circle you lead with the rudder.. you dont start rolling first.

Keep at it you will get it.