Angelisagemini,
I currently keep my housing fund in a taxable Vanguard account invested in index funds.
When I withdraw the money, I'll have to pay a 15% tax on the capital gains (if my eventual sale price is higher than my purchase price, I'll pay a 15% tax on the difference). I also have to pay taxes on dividends earned each year.
Your Roth IRAs, Roth 401(k)s, and regular 401(k)s operate differently. They're pots of money that hold your retirement investments, and if you take money from the pot too early or for an unauthorized expenditure, you are indeed penalized.