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Q. I think his RA compensation would be considered 'earned' income and I shall be able to fund his Roth IRA account, correct?
A. No.
Q. How do I report this as income on his 1040 without W2/1099/1098-T?
A. It's not reportable, as income.
Generally, undergrad stipends, even when taxable, are not earned income for IRA contributions (grad students are handled differently). Furthermore, on-premise room and board, where there is a requirement for the "employee" to live there is usually tax free. That probably explains the lack of a 1099, W-2 or 1098.
