The prosecution will call Tyler Robinson's roommate and alleged lover as a witness in his murder case ... TMZ has learned.

As you know, Robinson has been charged with allegedly shooting and killing Charlie Kirk at Utah Valley University in September.

New legal docs, obtained by TMZ, indicate Tyler's roomie, Lance Twiggs, will testify in the murder case.

According to the docs, Twiggs will submit a video-recorded interview with the prosecution as testimony ... but Robinson's lawyers are requesting his roommate appear in-person, since they say he's a "material witness."

Robinson's attorneys argue that he has the right to confront and cross-examine Twiggs at the preliminary hearing ... which he obviously wouldn't be able to do if Twiggs' testimony is pre-recorded.

The docs say prosecutors would be using the video interview to "authenticate alleged electronic communications" between Robinson and Twiggs.

As you know, Robinson allegedly confessed to Twiggs that he'd killed Kirk and ditched his clothes. He also allegedly asked his roommate not to cooperate with the cops.

Robinson is facing the death penalty for the alleged assassination. In April, he asked the judge to ban cameras from the courtroom ... but his request was shot down.