Roseum Elegans is a tough, adaptable rhododendron. They should do fine in full sun as long as they receive enough water. Protecting them in the winter with burlap or other type of screening is a very good idea for the first two or three years. As for the dark green leaves, rhododendron growers often use iron supplements to produce very deep green leaves to make the plants more attractive to potential buyers. Don't be surprised if the leaves revert to a more normal medium green color once planted out.

I have Roseum Elegans in a location that gets several hours of direct, southern sun during the heat of the day (NJ/Zone 7), but shaded by maples for the rest of the day. Make sure that you keep up with the watering (especially in the first few growing seasons), they are relatively SHALLOW rooted so not the best drought tolerance (but our summers tend to be wet and humid which is a plus). MULCHING is a most!

This is a not uncommon dilemma for rhododendron lovers. As akmainegrower said, if you really want it in that spot, you could always shade it with some burlap for the first few summer months (JJA)..and wrap for the winter months (DJF).

I suspect it's one of the most sun tolerant older varieties, I see big ones in open sites all around the lower Susquehanna valley and 'Harford Hills' as they are called....but this is a fairly salubrious climate by low elevation east coast standards - there are wild Kalmias self-seeding in almost full sun if you know where to look for them, and probably some of the southeastern most (again, low elevation) native hemlock stands. It doesn't show up as being cloudy on official NOAA cloud cover maps, but I've read more than one online post from someone on a site like city-data bemoaning the northwestern shore (of the bay) for always been cloudy.