iTunes Radio has been renamed to just Radio. You create a station by searching for a song, artist, etc. To the best of my understanding, everything under the Radio tab on iTunes/Music is free for all to enjoy, including Beats 1 and the curated stations.
+1
Also, all the custom radio stations that I created in iTunes Radio remain there in the new-fangled "Radio". Apple Music Radio is just iTunes Radio renamed plus Beats 1 as a new station. That's the way to think of it.
The thing that's better about Apple Music, and whether you call it a "Radio" feature or not is really just semantics, is this:
If you created "Billy Joel Radio" in iTunes Radio you'd get a custom station that played Billy Joel and a bunch of other artists with similar styles. Now when you just search on "Billy Joel", up will come the same ol' "Billy Joel Radio" but also you'll see things like "The Essential Billy Joel" and "Billy Joel for Beginners" which are (in effect) radio stations too but all they play are Billy Joel songs (no other artists) and they playlists are all curated by humans (so you get really good tracks and no filler).
To me, this is the best part of Apple Music's promise of "unifying" all these different apps. Just searching "Billy Joel" brings up a Pandora experience, a Spotify experience, and my personal iTunes Library experience all on the same search result, all on the same screen, each just a tap away.
BJ