Reminds me of the sort of thing that used to be advertised in the Sunday papers years ago. A bolt on roller drive electrical assist unit with rechargeable batteries etc. long before e bikes were a thing. The roller seemed to be its downfall, slipping at the slightest hint of rain, and poor motor power that never lived up to its promise to get you up hills.
Perhaps Rubbee have overcome all these drawbacks with modern electronics but none of their reviews in that link look convincing. If I was in the market for that sort of thing I'd let someone else (or a lot of someone elses) be a test pilot with their own money to get some feedback first. Curious that if they've supposedly been around in some form or other for so long that we've only just heard of them.