What I've come up with is parallel jaw pliers and needle files. Before using my parallel jaw pliers, I did take a big file and file the ends flat and shiny. I didn't want the pliers to mar my jump ring.
Twist the jump ring open, open enough to get a small file in there without touching any other part of the jump ring. Place jump ring in the pliers with the open end perpendicular to the top of the pliers. I look out the window, to get a clear and bright view of the end of my jump ring in relation to the end of the pliers. To make this process simpler, I did ben the top of the jump ring (cut side) flat. This allows me to line up the ends for a better solder seam. After flattening, it looks like a "D". After soldering, I use a mandrel and a nylon mallet to round it out again.