A mountain bike will never become a road bike. However, it can become a great drop bar mountain bike that is very capable of riding on roads. It's a much easier conversion too. All you need is a pair of slick tires for your current wheels (1.25, or 1.5 if roads are rough), a pair of drop handlebars, a pair of new brake levers, and a pair of bar end shifters. Friction shifting will make this job much easier. The stem will probably have to be swapped out to get the riding position right.