Softly-softly is the way forward. If he's not ready to settle himself to sleep yet then he needs to learn that gradually, so take your time with a new routine.
I'd start with picking a good time one evening - if he generally has a 12 hour day but only got up at 9, he's going to fight a 7pm bedtime. (Things to do start to come together re wake up and sleeping time, but there may be one day where you bite the bullet and get him up at 7/8am, earlier than he wants, to try and re-order his day)
Then introduce the idea of bath, pyjamas, bottle, teeth, story, for example - but keep rocking him to sleep, if that's what he wants.
Then once you think he is understanding that bath/bottle/story means it is time for bed, you can work on not rocking him to sleep.
Other posters are right and the bath etc is there to create a sleep cue. DD is similar to their DC, she sometimes even announces it is bath time when she's getting tired and overwraught. She's much happier once she realises that we're on the wind down to bedtime.
As with anything, it takes time for DC to learn what is going on. He will get there, but changing everything at once is probably too ambitious. Just focus on a bedtime routine, and work on the self-settling later.