Should I contribute to a Roth IRA of I don’t know what my income will be.

I’m a travel nurse currently making a rate of 130/hr. If I were to continue making this much, assuming rates don’t drastically decrease I would be ineligible to contribute to a Roth IRA. There’s also the possibility that my rate decrease and I’d be fine to contribute either way. My agency does not offer a retirement plan. What should I do as far as investing for retirement if I’m unsure if I’ll be allowed to contribute to a Roth by years end?