Van Halen is an American hard rock band formed in Pasadena, California, in 1972. From 1974 until 1985, the band consisted of guitarist Eddie Van Halen, vocalist David Lee Roth, drummer Alex Van Halen, and bassist Michael Anthony. The band went on to become major stars, and by the early 1980s they were one of the most successful rock acts of the time. 1984 was their most successful album.
A temporary reunion with Roth (1996)
David Lee Roth called Eddie to discuss what tracks would be included on a planned Van Halen compilation (work on which had actually begun before Hagar's departure). They got along well, and Eddie invited him up to his house/studio. Shortly afterwards, Roth re-entered the studio with the band and producer Glen Ballard. Two songs from those sessions were added to the band's Greatest Hits album and released as singles to promote it.  In September, Van Halen was asked to present an award at the 1996 MTV Video Music Awards. They agreed, and on September 4, 1996, the four original members of Van Halen made their first public appearance together in over eleven years. This helped to bring the compilation to No. 1 on the U.S. album charts. However, unknown to Roth, Eddie and Alex were still auditioning other singers, including Mitch Malloy.  The band's appearance on the 1996 MTV Video Music Awards fueled reunion speculation. But several weeks after the awards show, it was discovered that Roth was out of Van Halen again. Roth released a statement in which he apologized to the media and the fans, stating that he was an unwitting participant in a publicity stunt by Van Halen and manager Ray Danniels. The next day, Eddie and Alex released their own statement, claiming they had been completely honest with Roth and had never suggested he was guaranteed to be the next lead singer.  Eddie Van Halen would later explain (in regard to the MTV Video Music Awards appearance) that he had initially been embarrassed by Roth's antics while on camera behind Beck, who was giving an acceptance speech for the award that Van Halen had presented to him. Immediately following this, the band had been taken to a backstage press conference where press queries about a reunion tour were met with Eddie Van Halen saying that he needed a hip replacement and would have to record an entire new studio album before any tour. In private Roth told Eddie to avoid talking about negative things like his hip and the two almost came to blows, thereby shattering any chance of a full-scale reunion.

Q: How did Van Halen reunite with Roth?
A: They got along well, and Eddie invited him up to his house/studio.

Q: Did Roth re-join the band?
A: Shortly afterwards, Roth re-entered the studio with the band and producer Glen Ballard.
Why was it only temporary?
But several weeks after the awards show, it was discovered that Roth was out of Van Halen again.
But several weeks after the awards show, it was discovered that Roth was out of Van Halen again.