You mean to contribute to a ROTH IRA for them? Well they need to have earned income to qualify to make a IRA contribution. So you would need to give them a W2 or they would have to file a return as self employment income. It doesn’t matter where the money come from to fund the contribution.
See IRS Pub 590-A IRA Contributions
https://www.irs.gov/pub/irs-pdf/p590a.pdf
