There are many ways to access the money before normal retirement age. Read
this.
We would need a lot more information to advise you properly, but here are a few guidelines:
1) If you get an employer match in your 401k plan, the first thing you should do is put in enough to get 100% of the match.
2) If you pay anything above 15% federal taxes, you should not be using a Roth as your main investment vehicle.
If you do a taxable account VTSMX is a good fund to pick, but you might want to diversify into large cap or mid cap as well.