RO has made a big difference to my beers. I get it from Walmart too. You just have to add salts. My standard is calcium chloride for malty beers, gypsum for hoppy beers, and chalk for dark beers. I always add a pinch of epsoms and sea salts for flavor and to supply needed micronutrients. That and I use a nutrient blend in the wort, I believe it has some zinc.
You could always dilute your water 50:50 with RO. I'd agree with the suggestion to have a water test, otherwise you're kind of flying blind.