Drop what you are doing and go get a collet style Lee Factory Crimp Die.
You will never have to deal with the case length issue common to roll crimping
If you are getting a bulge on the bottom I am not sure that's from crimping, it could also be a function of the plate or shell holder that pushes the shell into the die. Most don't allow the case to fully enter the die. If you're using brass between revolvers and finding that after resizing it will fit in one and not another an undersized die will fix it. EGW makes one:
Undersize Reloading Die, .38 Special
Fits all reloading presses that accept 7/8 x 14 dies. If the die is installed on a Dillon, you may want to put the lock ring underneath the tool head to secure the die.
www.egwguns.com