Re: Help! to root samsung s duos 2 gt-s7582
An update will fail if the phone is rooted, because updating a rooted phone can brick the phone. An unrooted phone (the way yours is now) will get the latest update that your carrier has for that phone. You'll probably (depending on the carrier) get updates up to 4.4.4. I doubt there well be a Lollipop update for it.
And no, rooting won't let you update it to Lollipop if the carrier doesn't release a Lollipop update. About the best you can do is see if there's a ROM for it on
XDA Forums. Some ROM developers will modify a ROM for a phone they have, even if the manufacturer hasn't come out with one (and they have to before the carrier can send it to you).