Roy Oréjon (Ralph Moleman Guacamole Guadalupe Hidalgo) Estrada (April 17, 1943, Santa Ana, California) was an original member of The Soul Giants, which became the original Mothers Of Invention. Although he was born in California, his Mexican roots were a running gag in the group, as can be heard on Holding The Group Back and The Rejected Mexican Pope Leaves The Stage.
He is also a convicted child molester, serving a twenty-five year sentence as from January 2012.
Roy provided bass and vocal for Freak Out!, Absolutely Free, We're Only In It For The Money, Lumpy Gravy, Cruising With Ruben & The Jets, Uncle Meat, Burnt Weeny Sandwich, Weasels Ripped My Flesh, Zoot Allures, Shut Up 'N Play Yer Guitar set, Ship Arriving Too Late To Save A Drowning Witch, The Man From Utopia, Baby Snakes, Them Or Us, Thing-Fish, You Can't Do That On Stage Anymore Vol. 1, You Can't Do That On Stage Anymore Vol. 3, You Can't Do That On Stage Anymore Vol. 5, You Can't Do That On Stage Anymore Vol. 6, Ahead Of Their Time, Civilization Phaze III, The Lost Episodes, Läther, Frank Zappa Plays The Music Of Frank Zappa, Mystery Disc, FZ:OZ, Joe's Corsage, and Quaudiophiliac; and to the Beat The Boots series disks The Ark (BTB), 'Tis The Season To Be Jelly (BTB), Electric Aunt Jemima (BTB), & Our Man In Nirvana (BTB).
After leaving The Mothers he formed Little Feat with Lowell George. He played bass on Ivan Ulz's Ivan The Ice Cream Man album (1970). and played with Captain Beefheart's Magic Band during 1972 - 1973.
Estrada was convicted of sexual assault on a child on October 27, 1977.  He served six years in prison after he was convicted of committing lewd acts with a child in Orange County, California in December 1994. In January 2012, he pleaded guilty to a charge of continuous sexual abuse of a child which happened in March 2008. In the plea bargain agreement, he was sentenced to 25 years in prison and is not eligible for parole.
"Freak Out" liner notes
From the "biographical trivia" section on the Freak Out! (1966) album:
... Moved into my recording studio, joined forces with Ray, Jim and Roy, schemed and plotted for a year, working in beer joints, blah, blah, starved a lot, etc... played a lot of freaky music & stayed vastly unpopular (though notorious). OWE OUR EXISTENCE to Mark Cheka for his initial encouragement and sterling example (and to a whole bunch of other people who are going to be bugged because their names aren't listed in detail, with addresses and pertinent facts about what they like about the government & their other fetishes). Ray used to be a carpenter and a bartender and sing with Little Julian Herrera & The Tigers (note the falsetto part in 'I REMEMBER LINDA')... been singing R&B for ten to twelve years. Jim got fired from some idiot band in Kansas, forcing him to move to California. Lucky for us. Seems he just couldn't get turned on playing " Louie, Louie" all night... it must have hurt him deeply when they rejected him. Roy is an asthmatic Pachuco, good-natured excellent bass player, involved in the R&B scene here for about ten years. He is unbelievably tolerant. I don't understand it. Elliot digs the blues. He has a big dimple in his chin. We made him grow beard to cover it up. He just got out of the Army. Lucky for the Army. THEY ARE ALL MUSICIANS.
- Zappa referred to Estrada near the end of Legend Of The Illinois Enema Bandit: "Wait a minute. This is for Roy Estrada, wherever he is. Wanna, wanna enema, e-nemààààà, wanna, wanna enema, e-nemàààà".