Hi J.,
I think it is is very good that you have already gone through the cry it out stage for him to go back to sleep during the night on his own. I had to do it for my son, now 8, and it broke my heart, then again with my youngest daughter, now 2 1/2, and we still have to do it occassionally (still breaking my heart everytime).
Now, it may be time to do it for naptime also. And sorry to say, he may be getting a little old for rocking. I know that is enjoyable for both of you, but it has to stop sometime, maybe that time is now?
I would keep rocking for now and see if he will cry it out to go to sleep, when that is under control, then start cutting out the rocking by doing it for shorter periods (5 - 10 min), and putting him in his crib while he's still awake.
Or perhaps music, or the nature sounds (they are very relaxing), something to keep him company? I used to use them for my youngest when we were away from home for a couple months when she was an infant.
She had a Fisher-Price water thing (at home) with swimming fish, music box, and night light. We never used the nightlight, but the music was on every time she was in her crib. The music lasts about 10 minutes, has a volume knob, 2 songs, and nature sounds. She used to turn it on herself (push button) by the time she was a year old, if she was still awake when it shut off. She used that until about 2 months ago, when I decided not to put any more batteries into it.
good luck, and I hope this helps at least a little. : )