The biggest cost with the Roth IRA is the buying of Mutual Funds, they usually have a minimum buy in. I opted to buy stock to fund my Roth since it requires no large buy in plus I like the research. If your really interested in Mutual funds and don't have enough to start one you can always try Exchange Traded Funds, (ETF's). These can be bought and sold just like regular stocks with the same basic principal of a Mutual Fund. They are focused on certain sectors of the stock market but have no fund manager keeping an eye on it .

A small example with Gold

Mutual Funds: Fidelity has a Fund, stock symbol FGDAX, which will invest in companies that engage in gold related activities. There are quite a few of those companies and a fund manager decides which ones will be bought and sold for this fund. These tend to have fees associated with them. Though there are some that have no fees, research to find out which ones. To get started with this fund you'll need $500 for the initial investment with an IRA or $2500 without.

ETF's; In the ETF world there is a fund, stock symbol GLD, which just follows the price of gold. No fund manager to buy and sell. There are fees here also just not as much as Mutual Funds, plus they are already factored into the price so you never see it taken away. The cost is currently 74.08 per share plus the trade fee. 7 bucks through Scottrade.

Stocks: With stocks you just buy one company or more if you so incline. I'll use Randgold Resources since I own this one, stock symbol GOLD, these guys just mine gold that is all. No fund manager, no fees. Cost is currently 35 dollars a share plus the trade fee.

So as you can see there are many choices once you start to invest. Mutual Funds, ETF's, and Stocks, of course there are the CD's and Money Market accounts, minimums there vary from $500-$5000 to start.