There is nothing specific but it is a general consensus that if your computer is rather modern, say 5 yrs or newer, it can handle anything roll20 can throw at it. The hardest thing that will get thrown at most computers will be the dynamic lighting and the 3d dice. Now if you plan on using 3rd party software (skype or streaming software) then you need to make sure your computer can handle that also. The reason for my statement about dynamic lighting and the 3d dice is that those are the main things that are constantly changing. All the maps get stored in a cache when they are first loaded (that will cause a slight lag at first if they are large) but after that there is not much resource requirement. I played with a laptop that had a 1.6 gig cpu and onboard video (due to it being a laptop) with 2 gig of ram. It lagged a bit at first on the maps, video, and mic with the dynamic lighting and 3d dice rolling but when I shut down the video feed and the 3d dice, it removed that lag. Still had a little bit of lag with the dynamic lighting but remember this was about a year or so ago also. The roll20 has grown much better since then.