Since the registered account is based on cash transaction, could not support margin, it does not allow you to short any securities/options which need margin to cover. For example, you sell put option, when the stock goes down, you need to buy back the stock at the fixed (higher) price. Your RRSP account may not have enough money to fill in your obligation.
Acutally, you can short options outside your RRSP account, and hold mondy inside. At Option Expire date, buy to close options outside, and purchase stocks inside. Your portfolio may have the same final results, only the tax concern may be different (you do not need to pay capital gain tax inside, but need to pay outside). Good luck!