Agreed with Mary. How many birds, what are the dimensions of your coop, how many l.f. of roost space, how high are those roosts? A pic would be helpful.
Your birds need to be trained to the roost. But first a bit of problem solving is in order to find out why they are not roosting. I would block off the nests at night, every night, and open them back up in the morning. If they do not then use the perches, I would place them on the perches at dusk every night, and continue to keep the nest boxes blocked off at night until the problem is solved. IMO, it is a problem, b/c birds allowed to sleep in and foul the nest boxes will make it so NO ONE can use them.