A risk reversal begins by establishing a bullish position by buying a call option and then sells a put option, also a bullish position, in order to pay for the call option. The entire risk reversal is usually done for little or no net premium, while the risk reversal may actually generate a small amount of premium since put options are more expensive than call options, everything else being equal (time to expiration, distance from at-the-money, and so on).
A risk reversal is a bullish position, and since it's short a put option, the trader has to be willing and able to buy the stock at the strike price of the put.