My suggestion is that you let the stronger rouleur pull on the flats - this makes the rouleur work harder while the weaker rider can maintain a higher speed than on his/her own. On climbs you follow your own pace, but the one finishing earlier goes down to meet the one still climbing and climb the hill once more. Going down I'd recommend that the technically best rider rides in front, and the other one tries to follow as close as possible - this way the technically more inexperienced rider can learn a trick or two.