you can pull out the money you put in penalty free less any realized gains
Your absolutely right. Any contributions made can be withdrawn, penalty free, as they have already been taxed. However, if you have the cash invested, and you paid sales charges or commissions, then you aren't recognizing the benefit of the investment if you don't hold them for at least a mid-term time horizon.
I'm keeping a small emergency fund on hand
If you think you consistently have 3-5 months expenses in a safe, liquid position such as checking/savings, you should feel safe to invest any excess cash.
Placing it inside a Roth gives it more of an opportunity to grow
True. But try to think of this as only in the mid-to-long term (atleast 3 years). Mind you, there are mutual funds that you can hold that are beneficial for less than 3 years, just make sure you know you aren't paying front-end loads, or back-end CDSC fees.