Hosting Tyson Vs. Roy Jones Fight

The Mike Tyson vs. Roy Jones Jr. fight just got a celeb host -- Mario Lopez.

We're told Lopez will be the emcee of the November 28 fight ... introducing the various fighters and tossing to musical acts throughout the evening,

In other words, it's not just a fight ... it's an event.

Sources tell us Lopez will be at the fight venue -- not hosting remotely -- and the production is already taking steps to make sure they adhere to COVID-19 regulations.

Lopez -- along with all of the fighters, trainers, production crew, etc. -- will most likely undergo rigorous testing leading up to the fight to ensure everyone is safe and healthy.

As for the musical acts, we're told producers are gunning for A-list…