In your next design, whatever it is, include R in the early discussion, share the idea and ask his opinion. Alright, I trust what you said that R is too dumb to catch your ideas let alone give you valuable opions, but he'd give bullshit to cover his ignorance. Now here comes the trick, what you should reply to his dumb suggestions -
"Roger, that's a brilliant idea! WE should definitely have it implemented in the next version." (Note, "WE" did the design, not I, not me me me, this is team work!)
In reality, do what you need to do, not worrying he would check if you really followed his stupid idea or not, since he is not able to, according to your previous description to his level of expertise. Then you made the new design a team effort. I'm sure everybody understand you are the main contributor, if everybody agrees with you that Roger is a dummy.
I bet your Indian manager Alalababamad would not downgrade such design, cause it is team work! If he is still not happy, bring him to the early discussion as well.
Is it so hard to compliment Roger and Alalababamad? In our great Chinese culture background, it is kinda disgusting. Hey, we are in America, let's do what Americans do.
