Yes. You can contribute to a Roth IRA or Traditional IRA regardless of whether or not you have an employer-sponsored plan. In fact, IRAs are a great way to enhance your savings.
While participation in a retirement plan does not change how much you can contribute to an IRA, it can affect whether or not you are eligible to deduct your contributions to a Traditional IRA on your tax return. As long as you have earned compensation, you can always make nondeductible contributions to a Traditional IRA and benefit from tax-deferred earnings.