I actually biked home tonight that way! 76th to Portland, Portland to Minnehaha Creek. The new bike lanes were v. shiny. The roundabout does not seem optimally designed, but if I take the outside lane it seems ok.
I am not sure how you could actually make a roundabout bike-friendly, unfortunately. The main things are to remember are to occupy the COMPLETE CENTER of the lane you need, and don't even let cars think about trying pass while you're approaching or in the roundabout. Installing BIKE MAY USE FULL LANE signs, and perhaps DO NOT PASS entering the roundabout might help. In any case, of course, keep a sharp eye out for cars entering the roundabout that might forget to yield to you. It's lit up like a Christmas tree, though; as long as you're wearing reasonably visible clothing, I think you'll be every bit as safe at night as during the day.
Glad you tried it out! I think Chicago Ave is actually a little bit more scenic, but the stretch around Diamond Lake is quite nice (the surroundings, not the bike lane configuration