Your claim is right and I also think you should be paid in full. The casino should have adjusted your stake against the max win but instead it didn't and hence should pay the full amount since they accepted the bet.
I have removed promotional materials supporting them for now. Hope they will hear you out and will pay you in full.
To be fair, according to their TOS they could have paid yahoo62278 nothing at all and instead refunded his bet. I don't this qualifies as a scam, more like the right thing to do would be to pay the full amount.
https://roobet.com/roulette?modal=terms[...]
do not warrant that the software and website are free from errors;
[...]
If there is a technical issue during a bet which our team can verify; you will be refunded for 100% of the bet amount.
[...]
However the site has quite a few glitches, even the TOS is full of grammar errors. They clearly need help debugging, which yahoo62278 is providing, so they should just pay up and thank him

Some sites do allow you to place a bet over max profit and some don't. The system we had in place allowed you to place these bets, but we've never encountered someone that has placed a bet that should pay over max profit like you have.
If yahoo62278 had lost, would he have lost the full amount or just the max bet amount?
All your points are completely valid - of course they could refer to their TOS and not pay a thing (as many gambling operators love to do by the way) - most likely they would love to do so but that would mean that all their marketing efforts in this forum went down the toilet...
Being completely honest though... (fun fact: the slogan is "Roobet - The honest online casino") - what are we talking about here? @Roobet You ACCEPTED a bet, somebody won, he needs to get paid --> as simple as that. There is actually nothing to discuss. PAY, fix the error and move on. I imagine visiting a casino, the dealer taking my 300 bucks and in case I won... "sorry max win is this but we were happy to take your money even though it was more than the max"... LOL
Side note: Yahoo is the one pointing these things out - I dont wanna know how many people are doing the same, losing while just not knowing what is going on... I dont think any player´s bet has been refunded by them in such scenario if he lost?!
Edit: There are casinos who accept bets over max profits?!?!?! What am I missing here? That doesnt even make sense to me?!
2nd Edit: Oh and I wouldnt call this a scam either... just unfair and unprofessional