I have tried the Rollei 50mm f1.8 Planar and I was'nt impressed...Exactly the same performance as a Pentacon 50mm f1.8 and the Pentacon is a very cheap lens (I paid just £3 for mine, including postage!).
Have tried numerous 50-58mm primes and the best of the best so far is my fantastic Canon FL 55mm f1.2.
Unfortunately, it has a 42mm registration distance so unless you convert it to EF mount you would be forced to use it via an optical FL/FD-EF adapter and that will ruin its image quality.
I converted mine to SA mount so I could use it at infinity on my Sigma DSLR's which like Canon EF cameras, also have a 44mm registration distance, without having to use an optical adapter.
There is another option you may not have thought about...Nikon lenses...The Nikon E-Series 50mm f1.8 Ai-S...Very sharp, great contrast, very small and lightweight, nice bokeh and yet it goes very cheap...Noticably better than the Rollei too.
If your budget is increased a bit then look out for the Nikon 50mm f1.4, 50mm f1.2 or 55mm f1.2...All worth a look and all will focus to infinity of the EF mount. Just get yourself a Nikon-EF adapter and you would be in business.
