Kyogo Furuhashi gave Celtic the lead in the 48th minute but Alex Iacovitti levelled with Ross County’s first effort on target 10 minutes later.
Malky Mackay’s side looked like they might frustrate their visitors but Jenz ran in to meet Jota’s inswinging cross and head into the roof of the net from six yards in the 84th minute.
Substitute Liel Abada wrapped up victory in stoppage time when he curled home from 18 yards.
On-loan Lorient defender Jenz had only been drafted in after Stephen Welsh dropped out through illness on Friday.
The 23-year-old German picked up a booking in a shaky moment in defence but looked assured on the ball and made himself an instant hero with the crucial moment of the game on a ground where Celtic needed an Anthony Ralston winner in the seventh minute of stoppage time last season.
Andrew Smith was in Dingwall and rates the Celtic players’ performances out of ten ...
9. Daizen Maeda
Seemed fated not to be for the wide man. Wholly wasteful in sending wide a header that begged to be buried, then was denied superbly by keeper Ross Laidlaw with a neat flick. Had a small injury so no shock didn’t reappear after the interval. 5 Photo: Craig Williamson - SNS Group
10. Kyogo Furuhashi
A first goal of the season that came with a precise finish to break the deadlock 48 minutes in was the highlight of a display that didn’t see the forward at his fleet-footed best. 7 Photo: Craig Williamson - SNS Group
11. Jota
The winger’s importance to his team seems to be growing by the game. An irrepressible figure, as evidenced by the fact he provided assists for all three Celtic goals. 8 Photo: Craig Williamson - SNS Group