You have it down perfectly....... small router, the correct bit (be certain that bearing always spins free on the shaft free of any glue or it will burn the surface)..... when the sides are done i use a belt sander to let the top surface level and true..... when you do put the top on and then trim it with the router just take a hand file and finish the edge for a finished professional look.
The roller you have is a good choice but most of the times i just use the block of 2x4 you have pictured and just bang away and even use it to slide along the edge to be certain that the top meets the edge perfectly.... pay very close attention to being certain the edge is perfect..... If you make a mistake you can sometimes get a small scraper in between and pout some thinners / acetone in between to get them apart.... I like thinners