What happened in 325 to me is a very sad time in the history of Christs Church, doctrines of the Church were decided by politics. There have been even more evil leaders of The Church than Constantine who was only a defacto leader but again, the leader of a church on earth does not make the church, but the doctrines make the church.
It is hard to have it both ways, either belief in the Lord Jesus Christ saves us by His Grace or it doesn't. Because someone belongs to a church that some don't approve of is no measure of their belief in The Savior. The whole point of Protestantism is that you are saved by Grace alone. If some churches have ordinances, rules and laws that we don't accept it does not mean that the faith of their members in The Lord Jesus Christ is not real or accepted. Either Graces saves or it doesn't.
If Grace saves then I know plenty of Roman Catholics and Mormons that are saved.
ON the Mormon side....no.
Those who follow the Mormon faith also believe that they can attain heaven through works (Doctrine and Covenants 58:4243; 2 Nephi 9:2324; Alma 34:3035; Articles of Faith, p.92). While they claim faith in Christ, they also rely on following the commandments of the Mormon Church (Doctrines of Salvation, vol. 1, p 188; Mormon Doctrine, p. 670) and practicing good works (2 Nephi 25:23; Alma 11:37) in order to achieve salvation. The Bible is very clear on this point, stating that good works can never earn the way to heaven (Romans 11:6; Ephesians 2:89; Titus 3:5) and that faith in Jesus Christ alone is the only way to salvation (John 10:9; 11:25; 14:6; Acts 4:12). Salvation by grace is incompatible with salvation by human works (Romans 11:6). Read more: http://www.gotquestions.org/Mormons-Christians.html#ixzz3SZu3WbKO
Are there saved Roman Catholics? Very possibly. However, those counting on Mary to help with their salvation, who appeal to Mary for their salvation, and who pray to Mary would be in doubt.
The Jesus of scripture most assuredly saves. Just because someone says Jesus doesn't mean it's the Jesus of scripture. God the Son. The Jesus of scripture didn't break the law of the Old Testament under which He was born by literally eating blood. The God of scripture doesn't give up what belongs only to Him to some "queen of heaven" or so called "saints". Jesus is not the brother of Satan as the Mormons believe in nor is He just one of many gods to be joined by many more.