guitarreverie

I'm very fond of playing the following progression: E minor, C, D, B. It has a little bit of a middle Eastern/exotic feel. I'm curious what scale I could use to solo over it? What key is this progression in? And what would be the number system for these chords? I very much appreciate any help, I'm new to music theory. PS: a good example of this progression is Desert Rose by Sting (in a different key though).