The wicketkeeper-batsman hit 125 off 110 balls and helped New Zealand A post a decent score after earlier being in trouble at 55 for four.
Todd Astle chimed in with 63 and the legspinner also captured the wicket of Unmukt Chand (4) just before stumps to have India A 6-1 and still 304 runs behind.
The first day of the match was lost to rain but the surface had dried sufficiently to allow play last night and New Zealand opted to bat after winning the toss.
Three cheap wickets from Jalaj Saxena and a run-out saw New Zealand in a precarious position at 55-4 but Ronchi, who has played limited overs cricket for Australia but now qualifies for New Zealand, and Jimmy Neesham (27) put on a timely 50-run partnership.
Astle joined Ronchi at the wicket with New Zealand at 106-6 and they added 146 for the eighth wicket to take their side through to 252, with Ronchi bringing up his century in the process.
The 32 year-old, who found the rope 16 times and hit four sixes, said it was pleasing to make a strong start to the tour.
"It was really good to make some runs from a personal point of view, but with the position we were in it was good to have a partnership there with Toddy," Ronchi said.
"I think we're in a fantastic position with 300 on the board and them one down overnight. Now we've just got to focus on bowling well on a flat wicket and take our opportunities."
Mark Gillespie added the finishing touches with three late sixes to make an unbeaten 21 from 11 balls, before the innings came to a close after 77.3 overs.
India faced three overs before the end of the day, with captain Tom Latham's decision to give Astle the new ball a success.
Play resumes today at 4pm (NZT).
