I think you have it right. I have not actually incorporated this into a Vera scene as yet.
In the Vera scene's LUUP tab, as you suspect, I would add the following (with the assumption that my Roku is at ...235):
local http = require("socket.http")
-- 5 Second timeout
http.TIMEOUT = 5
-- The return parameters are in a different order from luup.inet.wget(...)
result, status = http.request("http://192.168.0.235:8060/keypress/Back", "run=run")
A little heads up, when testing this elsewhere, I found that not all of the commands that were supposed to work actually worked. "Back" was correctly responsive, however. Where I originally found this approach, the OP advised on setting the Roku into Developer mode first. I did not see any reason that would be necessary and did not do this myself, but it could explain why I did not get all commands responding correctly. Also, if you just try the above URL in a browser window, it won't work; it must be by invoking http POST.