I remember watching a time machine movie in the 90's, but I suspect the movie was from the 80's. I only recall some elements of the storyline. There was a kind of time machine that got out of whack because of a power surge in the nearby power plant. As a result, people from several different time periods start to appear in the present. In particular, I remember there being Roman soldiers. I think the time machine was in a high school, but I don't distinctly remember whether that's the case. The movie was possibly a Disney TV special.
My Science Project (1985)?
It takes place in a high school, and has people from different time periods appearing in the present. Here is the full movie from YouTube. At 68:30, you can see the characters from different eras appearing.
A high school student and his friend find a strange, orb-like piece of equipment to use as a science project, but must stop it when it begins to threaten mankind.