I couldn’t find anything about the following question. What is the Church’s stance on the Nag Hammadi and Dead Sea scrolls?
Let me at first refer you to a previous Q&A that answers part of your question: What is the Mormon Church’s view on the “new” scriptures that have recently come to light?
A search for “nag hammadi” on lds.org reveals only 9 results. Of these, most are articles or talks which quote from a translation. However, in the December 1982 Ensign, Stephen E. Robinson provides a good introduction to this sort of “ancient religious writings”. In it, he quotes from D&C 91, wherein the Lord answers a question about the Apocrypha. A part of that section states that in addition to containing truths, the Apocrypha contains many things which are not true:
4 Therefore, whoso readeth it, let him understand, for the Spirit manifesteth truth;
5 And whoso is enlightened by the Spirit shall obtain benefit therefrom;
6 And whoso receiveth not by the Spirit, cannot be benefited. Therefore it is not needful that it should be translated. Amen. (D&C 91:4-6)
“Accordingly, it has been the position of The Church of Jesus Christ of Latter-day Saints that the Apocrypha are not scripture, but that they may be of value if read with the Spirit.”
Stephenson ends his article with,
“Apart from the revelation about the Apocrypha in Doctrine and Covenants 91, no official statements about apocryphal literature have been made. Everything said about them, even by well-meaning Church members, is only opinion.” Background for the Testaments
A search for “dead sea scrolls” returns many, many more results. Among them is a good introduction in the February 2006 Ensign, by Andrew C. Skinner (at the time, Dean of Religious Education, Brigham Young University). The article does not add anything more regarding any official church stance on these ancient writings. The Dead Sea Scrolls and Latter-day Truth
As there are no further public statements available from the Church, we would be wise to follow the Lord’s counsel as given in D&C 91.