Generally speaking retro fitting road style handlebars is an expensive proposition; new levers, usually new shifters and the issue of mismatched cable pulls (i.e. cable disc brakes usually have long pull brake levers, as does linear pull rim brakes). Even if you use travel agents it can be trouble -or so my friend said who went that route and gave up on them. You'll also potentially have to add a new front derailleur too as road and mtb gear shifters have slightly different pulls (at least with Shimano that is).
Well, you get the picture -it's usually a lot of expense and faffing around. Can be done (I've done it) but probably not a high value proposition.