My parent contributed to my 2019 Roth IRA; I did not. On whose return is the contribution reported?

If the Roth IRA account is in your name, it should be reported on your tax return.

Your tax return.

A IRA contribution can only be made to your IRA is you have at least as much taxable compensation as the contribution, otherwise it would be an excess contribution subject to penalty that repeats every year until the excess is removed.   Parents sometime make a mistake and create and contribute to an IRA when the child's has no taxable compensation if their own.  Over years, the penalties can exceed the value of the IRA.

The most you can contribute to all of your traditional and Roth IRAs is the smaller of:

For 2019, $6,000, or $7,000 if you’re age 50 or older by the end of the year; or
your taxable compensation for the year.

(Taxable compensation is generally wages that you worked for - W-2 or net self-employed income minus the deducible part of the SE tax, but can include commissions, certain alimony and separate maintenance, and nontaxable combat pay ).

See IRS Pub 590A "What is compensation" for details:
https://www.irs.gov/publications/p590a#en_US_2018_publink1000230355