I think specificity should be emphasized in this discussion. Resistance training with weights, especially low rep high resistance will build muscle mass and strength, but the development will be most specific to lifting iron. In my experinece, the best way to gain cycling specific strength is to do a lot of climbing or try to turn a large gear. However, this can be stressful on the knees, so you should first prepare with some easy base miles and add the resistance component gradually.
Regarding weight loss, there is no doubt that you must burn more calories than you consume. However, this is an added stress to the body so you should be careful to get high quality food, lots of rest, and reduce the other stresses in your life, including training. The best time (and the hardest time for me) to lose is in the off season. Keep the intensity of your training low so your fat catabolism can keep up with your energy demands and the stress is minimized.
The most important thing is the displine to stick with a moderate and resonable program - good luck!