Can followers us the enchantment on a ring or amulet if I gave it to them to wear? ie. increase heavy armour

And do followers use Scrolls?

http://www.uesp.net/wiki/Skyrim:Followers#Enchanted_Follower_Equipment

I don't know about scrolls.

Followers will use Scrolls in thier inventory, and they seem to use the Scrolls at the worst possible moments in a battle. Ice Spikes in the back are bad for a Melee character during a Boss fight.