I would like to prevent user of specific role from posting more than 10 jobs on the front-office (not back-office). How could i proceed to do that please?
I've installed WP Job Manager plugin for posting jobs.
This is something you should be asking wordpress community about as they will either know the plug in you need or the code you would need and where to stick that code in your scripts.
Here's the first thing I found with a tiny bit of googling: https://wordpress.org/plugins/wpsite-limit-posts/