Is it easy to roast coffee in a grill? A resounding YES!
People overcomplicate matters when it comes to roasting coffee. One of the easiest ways to roast is in a grill. How do you do it you ask? Let's see ...
Put coffee beans in drum. Put drum on rotisserie rod. Put rotisserie rod with drum in grill. Turn grill on high. Turn rotisserie motor on. Close grill lid. Roast on high until you hear 1st crack. Continue on high for around 20 seconds then heat turn to medium low. Continue till your roast level is desired. If you want a City+ roast then roast until you do not hear any 1st crack anymore. If you want a Full City roast then roast until you hear the first sign of 2nd crack.
Note that the above is for roasting at drum capacity. If less than drum capacity then you need to adjust your heat by lowering temp down a bit at start and after 1st crack.