What would happen if you accidentally put like 2 gallons of deisel in the hydraulic oil tank which might be about 15 gallons and ran for say 30 minutes
Diesel has lubricating properties, otherwise your fuel injection pump would seize up. 2 gallons of diesel in 15 gallons is merely going to thin the oil a little, so you will find the hydraulics work faster when cold - but with the thinned oil, you're likely to see more hydraulic leaks.
I forgot to mention it's compacting equipment a roller
Drain refill and change filters. Will not ever get it all out but will have majority, no harm no foul and a early fluid swap.
Change fluid & filters and go back to work.