The Roth IRA was establish a few years ago by Congress as an alternative the standard IRA. Both were created as an incentive for individuals to make personal contributions for their retirement. Think "tax shelter".
First requirement to participate is that you must have "earned income" which for most people means a paycheck although certain kinds of self employment income can also qualify. The current maximum annual contribution is $3000 per year if your earned income is that much, otherwise it is capped at your earned income. Your parents, uncle or grandparents can make the contribution, it does not have to be your money. Second, there are restrictions based upon tax filing status and income level. I assume you do not make over six figures and that you file a "single" tax return so this should not be a problem. Note, you do not need to put in the max amount. One option could be to put in a fixed amount each month, such as $100.
Next issue is finding a custodian who will keep your assets. The common choices include: brokerages, mutual funds and banks. I would recommend that someone just getting started choose a mutual fund or fund family. Something to ask about is the annual fees (if any) that your custodian might charge. Anything above $20 per year should be avoided.... and zero is most cool. You can find a list of mutual funds in the March issue of Consumer Reports. Vanguard, T Rowe, Janus are some of the NO LOAD funds (no front end or back end commissions charged) that you can find on the
www. I further recommend that you choose a broad based stock fund, such as an S&P index fund which will give you market performance. I do not recommend individual stock picking or trading for someone getting started. An index fund requires very little "maintenance" by you... just check you periodic statements. Talk to three different custodians. Ask them for their "just getting started" materials, which are often very good.
Why mutual funds? Because you get "diversification" which means you don't put all your eggs in the same basket. Why the stock market? Over many decades you should expect assets to appreciate the most in stocks (also called equities). The last three years have been ugly, but that is a very unussual string of negative years. IRA investments for a 19 year old should be thought of in decades.
Contributions to a ROTH are not deductable. However, many years from now you can withdraw tax free. If you put the max amount in each year for the next 40 years... then you can retire at age 60 with a nest egg that will probably exceed 1 million dollars. Marry someone who also thinks about their future and you will have twice that amount. You don't have to be a doctor, lawyer or MBA.... Congress created this great tax shelter for everyone. The tax sheltered compound growth of you assets is a key value of the Roth.
Two final notes: You did not say if you are just working or going to college or both. Remember that IRA money is locked up for a long time and that there are penalties for taking money out early. Be sure that you have some "emergency" money set aside in case the worm turns against you. Education is another big investment for the future and I hope you are pushing in that area as well.
Post again if you need more info or have questions.