@RISK Vs R. Monte Carlo simulation in R?
Monte Carlo simulations are very easy in R. The simplest approach is to write your own scripts that carry out the steps you need for your simulations. To construct these scripts you will need to understand what you are simulating, that is what is the distribution of outcomes, and what are you measuring about those outcomes. If you understand what you are simulating than writing these scripts is easy, but will require programming in R. If you are new to R and/or to programming then it will take some effort to get up to speed. In the end, you will probably understand your data, simulations, and results better. There are packages for Monte Carlo in R, but these are not packages that will do the simulations for you and would require as significant learning of R to be able to use (as much as writing your own scripts). 

I suggest reading more about conducting Monte Carlo simulations in R. There are many resources online and offline, such as this book or this tutorial.