"Can I use that plate yet?" "Sorry, no. The cook has a roast on the plate."
I took "a roast" to be short for "a roast dinner". Commonly used in British English to mean any form of meal where a roasted meat (e.g. duck, beef, pork...) is the centrepiece. So no problems here with that term and am interested/happy to see that it's also used in Italian :)