I am not sure what you see is just because of roach. I have a feeling it was more due to a flatter sail shape which is much better for speed than a deep sail - particularly in flat water.
How much time do you spend tuning the rig? Getting the correct prebend in the mast may help move the draft forward with more halyard tension and cunningham.
Also the roach on my main also overlaps the backstay by about the same amount so not sure it really has more roach.
I think it can work but you better have a sailmaker that will invest a lot of time in getting it right. If you don't then I would stick with OD sail sizes since we all know they fit the rig once the rig is tuned and there is a lot of info on how to tune to the sails.
New sails are going to be much faster than what you have - period .
