My kids are 12 and 13, and I hire them, especially during rehabs, not so much during regular landlording bc there isn't much to do as a landlord (collecting rent and minor repairs, once in 6m air filter changes and such). I do take my older one to do 'landlording tasks', so she can get exposed to 'handling' tenants and the tenants know her, but she isn't compensated for that.
I do pay my kids during rehabs for painting, minor carpentering, cleaning, mowing, but they are not on a payroll and the payments aren't monetary, but in forms of some games, books, and other items they want to have.
Now, Roth IRA isn't something I contribute myself or plan on doing so in the future. Not sure I would be pushing my kids to contribute there. They each did get a CC this Christmas. But again, I'm more interested in them learning how to churn and sell tradelines as oppose to learning about Roth IRA contributions. 'Saving' isn't high on their priority list at this point.