My IRA is sharebuilder through ING. What does hold investments mean. Are you talking like specific stock?
If you have your IRA at Schwab, Vanguard, etc. then you can invest the money in stocks, bonds, index funds, ETFs, etc. Generally the rule of thumb is to get your maximum employer 401K match first. After that, max out your IRA (and decide whether you prefer a traditional IRA or a Roth). Third, max out your 401K. This will get you the best tax advantages and lowest fees, since your IRA fees will most likely be lower than your 401K fees.
The maximum you can contribute to a IRA is $5000 and the maximum to a 401K is $17,000. That's per person, so when your girlfriend graduates and gets a full time job, she can contribute the same amount separately, even if you are married at that point.
Keep in mind that with a Roth IRA you can access the contributed funds before age 59 1/2 with penalty. You can access the interest without penalty if it is to be used for a down payment on a home, medical expenses, and some other things, as long as they follow certain rules. However, with a traditional IRA and a 401K there are penalties for withdrawing funds early, so if you plan to retire early, keep this in mind and plan accordingly.
You're already in a great position - congratulations! I'm impressed by what you've already accomplished.