A dc speed control will allow you to control the speed. It will typically have a speed control knob and a forward/reverse switch on its panel. You can either use a pair of pedals, one for forward and one for reverse, or switch directions at the panel and use a single pedal for off/on.
Attempting to control the speed with a rheostat type foot pedal isn't a good idea. While its easy to keep a pedal depressed and move around a bit as you feed the stock thru the rolls, its near impossible to hold a variable speed pedal at a constant rate when any body movement is necessary. If you're in the middle of a tight turn, or any other situation that requires a low speed, the least bump of your foot on a variable pedal will result in a scrapped part most of the time.
I assume you have a gear motor rather than just a standard DC motor. Somewhere around 20 rpm is the upper end for speed on a bead roller with 2" rolls. This gives you a speed of about 10 feet per minute. Most work is going to be done at half or less of that max speed to maintain good control of the part. A gear motor is the only way to achieve smooth operation at 5 to 10 rpm.
