Generally speaking, a Roth account is one in which the monies placed into the account have already been taxed AND additional monies earned by investments within the Roth account are tax free.
A Roth IRA affords some key tax benefits for savers, chiefly the ability to make 100% tax-free withdrawals in retirement. Typically, the scope of investments available through an IRA is determined by the company that holds your accounts. A self-directed Roth IRA, however, can offer more choices for building a portfolio. One of these choices is a note.
As an example, your self-directed Roth IRA might own a 100K note written at 7% interest over 15 years. Not only will the Roth IRA be re-paid the original 100K, the IRA receives $61,789 in TAX-FREE interest earnings. Ka-Ching.
There are a number of well-regarded Self-Directed IRA custodians. Two of them with whom Partial Notes .com is familiar are Quest Trust Company (https://www.questtrustcompany.com) and Tax Free Future (https://taxfreefuture.com/).
Note: other self-directed accounts can also be used to purchase notes: HSAs, Solo-401Ks, Coverdell IRAs, and others. See a self-directed IRA custodian for specifics.