Ludmila,
Bigger Pockets provides the world's best place for real estate knowledge. But being honest, we as a community, don't know much about traditional investments like Roths. I encourage you to verify all of this with a certified financial planner. Still, here are my take.
You can take your contributions out of a Roth IRA without penalty or taxes as long as those contributions have been in your Roth for 5 years. Note that this is limited to your contributions, and is not true for any return those investments have made.
You mentioned part of a key point: Taking money from your Roth will indeed decrease future Roth earnings. The obvious side of this is simply returns. But just as big of an issue is taxes... Roth IRAs are extremely tax advantaged!!! Real Estate can be tax advantaged as well, but you're still moving money from a tax advantaged situation to one that probably doesn't have the same level of tax benefits. For this reason, it's preferable to invest new money into real estate (though I know this is not always an option).
I'm also very worried by the comments you made about your Roth returns last year. Generally speaking, IRAs are long term investments, and it should never ever matter what happens over a 12 month period. How have those investments done over the last 5 year, or 10 year period? Or, more importantly, does your current allocation still align to your long-term goals?
I may be reading between the lines a bit, but it sounds like you may be considering using capital from your Roth to avoid taking out a mortgage. Is that true? If so, I would generally advise against this. Using mortgages is one of the big reasons that real estate returns can be so high.
Should you take the money out of your Roth? That's a decision that you need to make for yourself. It's a big big decision, and one with huge long-term implications.
Either way, Happy Hunting!