Hey I currently have two Roto Grips. The r the cell, and the mutant cell. I'm looking to get a hammer that's about 3 boards more aggressive. I use to have the black widow and I miss that ball but it's a retired ball ATM. So I need help lol. I'm looking to replace the mutant with a more aggressive ball with a late hook. And I want the same curve app term except 3 boards more aggressive from the cell. So if u could help that would b great thanks! 

For what you are looking for, I would recommend the following for you:

Cold Blood (earlier with a strong continuous backend motion)

OR

Amp (cleaner through the front part w/ continuous motion in the backend - is about 4 boards weaker than the Cold Blood)

OR

Absolut Hook  (released today) - This is about 1-2' earlier than the Amp with the same backend motion of the Cold Blood...

Hope this helps with your question....

the Hammer line is very good, they have some great pieces
i switched from Storm/Roto a few years ago and the Ebonite brands have many options to fit your game.
The EBI group has 50% of the bowling balls sold in the world
Storm/Rot - 25%
Brunswick - 25%
there are a few other stragglers in there, but the overall numbers are pretty close
EBI has some really good R&D and is putting out some awesome pieces
Dont know why you would want to go back to roto

I tend to throw both Roto and Hammer pieces. I know they list the First Blood as a late breaking backend piece, but I have as yet to see this movement. It does carry well,  but the Cold Blood in my eyes is a much stronger ball. It reads the mids strongly and has a bigger backend to me. Now, having said all that neither of these balls can touch my Hammer 3-D Offset in backend movement. LOL! (just sayin')

P.S. The fact that the EBI group sells 50% of all balls in the world is because it umbrellas 4 different companies, duh! I think that works out to 12.5% per company?Hmmmm. When presented in terms of numbers, kind of makes Storm/Roto and Brunswick look pretty good as well! (just sayin')