If you hate sanding (so do I), and just want to break the edge a bit, I'd highly suggest getting an inside-curve cabinet scraper and learn to sharpen it and draw a hook. Properly sharpened, this method has a lot of advantages over a block plane or a ROS. ROS can be very agressive on corners, and it's easy to very quickly remove more than you wanted to. It's also not so easy to get a consistent roundover along a long edge.
A block plane is a good method, but the configuration of the boards in the project and/or how figured they are sensitively affects whether this is a good tool to use for the purpose or not. Occasionally (often) you find that the board's configuration in the project makes it impossible to plane with the grain, or the wood is figured enough that there isn't a "plane with the grain" direction. Under those circumstances, you can tear out an edge pretty easily. A scraper, by nature of its cutting angle, doesn't do this. And they're dirt cheap - about $8 at woodcraft.