Gifts are never taxable income.
It doesn't matter how you fund your Roth, as long as you did have at least that much income earned from working. Once it's in your bank account, it doesn't matter where it came from. If you were paid $20,000, and someone gifted you $5000 for your Roth, that's the same as if you put $5000 from your job into the Roth and someone gifted you money for living expenses.
But, you can't contribute to a Roth unless you did earn money from working.
