The First Step Is the Hardest
Try to balance your body on the center of the drum throne (the drum throne should be without the back rest) so that you would be able to lift your feet of the ground for at least a couple of seconds, practice it by lifting both feet off the drum pedals, while keeping both arms led all the way to the sides of your body and back - parallel to the ground.
Practice method described above till you get comfortable lifting both of your feet off the drum pedals with your arms in any position (back to the sides and front of your body)
Now start practicing lifting your feet while performing a slow non stop single stroke roll across all of your toms (left to right and than right to left) - you may add tempo to the single stroke roll after you will get comfortable.
When you will get comfortable doing the above exercise you may start practicing #3 above with the double stroke roll across all of your toms (left to right and than right to left).