It's not a losing game if you don't use your money to play (the coupons dageroth referred to), and you get to keep any money you win. (The 'hack' is you weren't supposed have ~€800 worth of coupons.)
The house edge for a Red/Black or Even/Odd bet in roulette is about 5%. Meaning that if he on average walked out with €400, you would expect that he walked in with €420 in coupons