Reporting your gambling winnings and losses on Schedule C as a professional gambler might reduce your MAGI for Roth IRA purposes because the losses on Schedule C will reduce your AGI. The only way to see whether it would allow you to make a Roth IRA contribution is to do a trial tax return. And note that you cannot claim a net loss from gambling. Even on Schedule C your losses cannot exceed your winnings.
But to file as a professional gambler, gambling has to be your primary occupation. If you have significant income from a job or another business, the IRS is likely to say that you are not a professional gambler. Also, check with a local tax professional concerning your state's rules about professional gamblers. Each state has different rules. The state might not allow you to file as a professional gambler, even if the IRS does.
