What sort of roast are you doing? If you do the joint/chicken in a roasting bag it will help to infuse the flavours: If it's chicken you can put 1/2 a lemon or onion in the cavity and cover with mixed herbs, if it's pork you can coat in herbs, for lamb you can cut slits into the joint and insert slithers of garlic then top with rosemary, for beef you can marinade in a small amount of red wine overnight.
I hope that helps a bit