Exercises to enable Rolling

[Quilb]

Hello,

Just a quick question. My martial art like a lot of others requires rolling (Rolling Diagonally across the spine.) This is something i would like to be able to do well. However when i do try rolling i occasionally get pain down my sides, specifically on the side opposite to which shoulder i roll over.
Also i have a lack of muscle on my shoulders so when trying to roll i also feel like i am grinding my shoulder bones into the ground.

Any tips? One thought i had was to strengthen my shoulders to have a layer of muscle there.

Regards,
Quilb