Yes this would be easy. But one problem with the API right now. Until Riley gives us access to the Roll20 dice mechanics within the API we can use a method that is not supposed to be very random (compared to Roll20's methods). We can output dice commands to the chat window as well as intercept get result from dice rolling commands, but I'm not up on doing that. One way I might tackle the problem would be to write a chat window command script. So you would type in the chat window (or later make a macro of course) ! and then some commands and your dice rolls. The script would roll the attack itself and figure out if it hit and by how much. Then it would send a message to the chat window to roll the damage dice and also tell you you hit and by how much. Really anything is possible. You can get stats from character sheets, info from tokens, etc. I made a stop watch out of a token. I used the three bubbles to display hours, minutes, seconds. Then had three macros to stop it, restart it, and start it for 30 seconds or whatever you want. And I'm just a newbie at javascript. There are some guys that really know what they are doing in the API forum. You might go there and detail exactly what you want or what system you are using and maybe someone will choose to write a script for it. I might, but right now I'm doing three different scripts, one for Edge of the Empire RPG for someone. What I really want is access to the dice rolling of Roll20 so I can make any kind of dice I want and then output them to the chat window formatted in any way I want.
