The usual reasons to go for the 401K plan rather than a Roth are 1) the employers match, 2) the higher contribution limits let you put more in, and 3) it can be less costly especially if subsidized by your employer. The match makes the 401K preferable, although aftertax Roth and pretax 401K are equivalent in retirement if tax rates are equal.

If your resources at this point do not allow more than the $3K max contribution to the Roth, then Roth is OK. But you do want to get started as soon as you can. So be sure to pay yourself first whenever you get a chance. Increase your contributions by putting at least part of future raises into one of the plans.