Which materials used for plates absorb microwaves?
In my experience, vitreous ceramic (Luminarc) heats up a lot in a microwave, usually ending up hotter than the food. But I cannot tell you if it has some advantage over heating the food in any other material. 

Also, if you really want to eat crispy roasted food, the microwave is probably the least suited heating method for that. I have never used the suggested "crusty plate" but I wouldn't expect much of it.