Roller-cams are NOT U-Brakes! They use the same mounting posts but are not the same brakes. U-Brakes are like the frame mounted center-pull brakes. In addition, the post for canti's is different than the post for RC/U-brakes. Canti posts are mounted inside the diameter of the rim, RC/U-B's the post is mounted outside the rim diameter. Frame "surgery" would be needed to switch from canti's to RC/U-b. I’m going to offer you some tips on how to adjust the front and the back roller brake found on the Shimano Nexus systems.
What matters most is to find the perfect tension for yourself, so when holding the brake and pressing in the handle you have to decide what tension you want, like if you want the tension to be hard or you need to press harder. You can do this by adjusting the brakes in two positions.adjust the roller-cam bicycle brake
The first position is on the brake lever. These are more for finer adjustment so you turn the knob on the lever outwards to put more tension on it or by pulling it outwards you can see that the ring moves as well so move that back until it’s against the knob flush and at that point the brake is adjusted but that is just for minor adjustments.
The other place to adjust the brakes is on the brakes themselves. For this, you will require a 10-millimeter wrench so if you look at the knob, the first thing you do is to loosen the nut. After you’ve done this, you can adjust the knob by pulling it up. Then you basically put more tension on the cable and make the brakes a lot harder to press in. Or by pulling it down, you can put less tension on the cable. When you are done with that, move the nut all the way down. You can do this by hand first and then tighten the nut up with your thermal meter wrench. How much tension is suggested? Squeeze the pads to the rim with your hand. Pull the cam out from between the roller wheels. Now one brake arm can be pivoted away from the rim and the wheel should drop right out. Ultimately, the roller wheels should be just at the top of the bulge in the cam when the brake pads first make contact with the rim. And you’re good to go.adjust the roller-cam bicycle brake
The brake adjustment for the rear brake is similar to the front brake. If you look at the brake itself, you can find a knob and the same nut. A 10-millimeter wrench is needed. Bu loosening up the nut, you can basically move it up and move more tension on the cable or move it back to put less tension on the cable. When you’re done, move the nut by hand and tighten it up with a wrench.
Road levers are perfectly compatible with Roller-Cam brakes - they use the same pull ratios. The only thing to worry about is if the Roller-Cams are on the rear, underneath the chainstays (as was stupidly-popular in the late 80's). If so, then you probably won't have any place to put a barrel-adjuster underneath the bottom bracket, so you'll need to get some road levers with integrated barrel adjusters or find a clever way to an in-line barrel adjuster.