Yes. Radiologists must be licensed physicians, so they can write prescriptions. In theory, they could write for any drug. However, do to the fact that most have been away from clinical medicine for quite a while, its probably best to limit prescribing. The most commonly prescribed drugs by rads are probably pain meds due to the fact that most radiologists do procedures (not just the interventional rads). If you are in interventional, you may also prescribe some antibiotics (also anticoagulants and thrombolytics for inpatients).
If you're asking about writing prescriptions for friends and family, its definitely a questionable practice, but technically seems to be legal. Most only do so in rare special circumstances with relatively benign meds or meds that people have been on for a long time (albuterol refill, ocp, etc.).