You need to visit an estate planner. In some states it's perfectly possible to set up a trust for the child which you can start contributing to immediately. Then when the child reaches working age (14 in most state) and does have an actual job that pays income the IRS will want to know about (a W-2 or 1099-MISC job), then you can have the trust set up so that $5500 a year, or his total earnings for the year (whichever is less) transfers from the trust to a ROTH IRA in the name of the child.
