I used some in my stream, mainly where I could not have rocks, I have such a slope had places where rocks would not stay in place even in the stream. Over time the ror weathered, it looks very natural, Just keep straight edges either from showing or make the edges wavy when you cut it. Also crumple the ror makes it look even better.
Go by the color of your rocks, I used the brownish color since most of my rocks are tan/brown
posted this in another thread about ror, posting it here too
I did find one picture on my computer, I changed computers right before coming down here, all my photos are at home.
You can see the ror under the rocks along the bog edge, I cut it into pieces attached it with some pl roofing goop, made the lower edge, round, or with dips, angled etc Made it blend in and look like rocks below the rocks along the edge. It is a vertical edge 2.5 feet tall. The ror edges go below the water, it has been installed for a few years now.