There's no definitive answer to this question since wealth is relative. A low roller in Vegas might have a lot of money compared to the average person, but very little compared to a high roller.
That said, a low roller in Vegas would probably need to have at least a few thousand dollars to be considered wealthy. This is because a low roller would likely only be playing at lower stakes tables, where the minimum bet is usually around $25. So, if a low roller had $1,000, they could only play for 40 minutes before going bust.
Of course, there are other factors to consider, such as how much money the low roller has saved up and how much they're willing to risk. But ultimately, it would take quite a bit of money to be considered wealthy as a low roller in Vegas.