Great, if a work phone is required by a company, let the company provide it and leave that one alone. Do you have to supply your own work computers or other equipment "required" to do the job as well, outside of contract work?
Unfortunately that assumes the employer will provide the phone rather than going "this guy can't do his job because his phone is rooted?" and hiring someone else. Or that the employer knows what rooting even is.
Most companies ask you to install work profiles and such only after your sign on. It would be exceedingly petty of them to fire you for something like that, especially at a tech company that will definitely have the money to provide ~$300 work phones