Yes there is no deposit, login or register button when we visit on the first time. I'm using my mobile phone though, the site fits in my screen very well. I just tried to place some chips on the board and the deposit option does exist after you place your bets and click the "play" button in the center of the roulette wheel.
It seems that it is an on chain roulette game where we play directly from our wallet but I wonder if it is an onchain game why admin uses the word "deposit". I think there should be FAQ page, at least give a "How to play" instruction so new users wont be so confuse.
Yes there is no deposit button and I don't why there's a 10 in balance after the site loads after that I played the roulette because of the balance that I see which is 10 but I lose so I tried playing again without balance but after I select the play button it redirect me to this site
https://lightning-roulette.com/deposit#5. In my opinion having deposit button is more appropriate rather than playing without balance and redirected to the link above.