Bit of a late answer, but I had to respond to this.
I'd take a different stance: This chord progression's tonic is D. In the D major scale, Em9 is the ii, A is the V, and B is the VI. So, it's D: ii-V-VI. The reason why I champion this particular view is twofold.
1: The prescence of a ii-V makes a whole lot of sense not only in jazz, but also in a more funk/R&B context. The B, being altered, is not diatonic, but rather can be seen as V/ii (a more jazz/classical view) or simply a VI chord (the vi but more interesting).
2: I've got a really good example:
The example (Michael Jackson's "Rock With You") uses these chords almost exactly, and what's more, the melody and everything else suggest very strongly that the tonic is D major! In fact, as soon as I read these chords off of this question I thought of this song.
If anyone wants to contest that the more traditional funk analysis is actually i-IV as a dorian move, that's fine, as the chords never play the I chord, but I find that in this specific context, the whole progression revolves around D. Another answer even mentioned that the chord progression sounds good with A7 instead of A. That's a smoking gun for D major! Even better, we can investigate this by adding all kinds of extensions and seeing how well the chord progression works.
Em9? How about Em11, the ii in D major? If I'm right this should sound different, but functionally the same. I checked, and it sounds the same. A7? How about A9 or A13 instead (V9 or V13)? These all seem to work well in that progression. B? How about B9? *(Yes, B9 isn't diatonic, but take the regular Bm9 and make its third major to get B9).
E minor, in my opinion, doesn't really feel like a resolution in this progression. B definitely doesn't feel like home when used in the context I'm describing especially. D major does have a great sense of resolution when played after the chord progression.
I'm not saying this can't have any other interpretations, just that my way is something I feel other answers missed and that this analysis shouldn't be overlooked.