The "approach leg roundabout" is kind of like what they have done at Glenmore and 37th Street SW. In this case, however, I don't think that it will work very well.
The one at Glenmore/37th diverts EB Glenmore to NB 37th traffic to a roundabout instead of allowing them to turn left. This eliminates the need for a dedicated turn signal, thus improving the flow of the WB through traffic on Glenmore
In short, the benefit lies with the WB traffic by preventing the EB traffic from holding them up by turning. This is the opposite of what the Royal Oak one proposes. The Royal Oak example is trying to improve the flow of the turning traffic by diverting it around a roundabout, without enough space between the roundabout and the lights to hold the cars that are going to use it.
I wish that I could explain myself more clearly. Of the proposals, I think that the double-lane roundabout is best option. But I am a roundabout fan with experience abroad, so my view is a bit idealistic because I know how they CAN and SHOULD work.