I was recently reminded of a passage in The Shepherd Of Hermas that I'd forgotten about. It's addressing people who consult soothsayers, false prophets, and the like:
"For no spirit given by God requires to be asked; but such a spirit having the power of Divinity speaks all things of itself, for it proceeds from above from the power of the Divine Spirit." (Commandment Eleven)
Michael Holmes' translation renders it:
"For no spirit given by God needs to be consulted; instead, having the power of deity, it speaks everything on its own initiative, because it is from above, from the power of the divine Spirit." (The Apostolic Fathers [Grand Rapids, Michigan: Baker Books, 2005], 407)
It seems that Hermas didn't think we should pray to the deceased or angels. In a thread here, I discuss another passage in Hermas that points in the same direction. Use the Ctrl F feature on your keyboard to search for "Hermas". The discussion is near the end of the thread.
That same thread also discusses a lot of other patristic evidence against the practice of praying to the dead and angels. Use Ctrl F to search for Justin Martyr, Athenagoras, Lactantius, and other patristic sources. In a post here, I have a collection of links to my material on prayer to the dead and angels, including other threads in which I interact with advocates of the practice.
A couple of things that should be noted about Hermas are that he's early and Roman. His work or portions of it are dated anywhere from the late first century to sometime in the second. And he lived in Rome and apparently was the brother of a second-century Roman bishop (according to the Muratorian Canon, though later sources make the less likely claim that he was the Hermas of Romans 16:14), so his background makes him harder to dismiss from a Roman Catholic perspective.