Every single time I have tried to make curved plates, I end up turning them into casing…
Anvils can be a little counter-intuitive to understand the first time around, but they’re actually pretty simple, to the point they tend to lead to a facepalm moment when you find the trick:
The small and big roll bending relate to the two bits at the left and rightmost end of the anvil itself. You have 3 choices: the flat anvil base (which you’re using right now), the big bit and the small bit. You’re supposed to smack your hammer on either one of those bits to get different results: [Big] roll bending will require you to smack your hammer on the bigger side, same for [Small] with the opposite side. And by the way with that I mean the actual bit sticking out, not the flat surface near those!
Oh yeah I recently did add a tiny graphical hint in the NEI Page for Anvil Bending, with an Arrow pointing at which Side you need to click.