Can I use reverse osmosis water for cooking?
A good RO system costs about $100,000 as advised to me by a hydrologist.  You may be better off with a good 3-filter (10 micron) setup.  RO is usually used for high volume of consumed water and doesn't get everything out (unless you have the $100k system). 

Before you spend the money, I would recommend consulting a local hydrologist and lab about other local tests they've performed over the recent times and what they've found in the water.   

You can also walk into the nearest Starbucks as ask them about the filters on their lines.  Regardless their coffee taste, they are usually strict about their water being good.  You may be able copy their set up and be happy with it.

As far as cooking and brewing with 'over filtered' water goes, it may be a better problem to have than unwanted stuff in the water left behind.  Some bottled waters such as Dasani have everything removed, then they add back some minerals to satisfy taste profiles [sales].

For cooking and brewing, you're unlikely miss the taste of the minerals in the water and more likely be happy about crispness.