Hot Chip, Mel C, KT Tunstall, Dynamo and Phil Daniels are among the stars who manned the sale at the Old Truman's Brewery in east London.
Items up for grabs included the Blur star's drumsticks, art by Pete Doherty and Russell Brand's trousers.
The aim is to raise £100,000 for mobile health clinics to help Syrian refugees and host Jordanians in need.
Rowntree collected more than 1,000 items for the Star Boot Sale in Brick Lane, with some items available to bid for online in an auction that will remain open for a week.
He said: "It was really good, we had lots of fun and everyone was smiling.
"The most popular things were the knick-knacks from the celebrities, people were falling over each other for them."
Some of the items, such as books, started from £1 while a gramophone donated by Coldplay has already attracted an online bid of £2,000.
Model Sophie Dahl gave clothing including a faux-fur Nicole Fahri jacket and a black Balmain jumper and Sir Bradley Wiggins donated a cycling shirt.
The refugee charity International Rescue Committee estimates there are more than 650,000 Syrian refugees in Jordan, of whom as many as 80% live in urban areas rather than in refugee camps.
Rowntree said: "It's hard to get basic healthcare services to those people, that's why mobile health clinics are so vital."
Blur drummer Dave Rowntree rounded up some of his celebrity friends for a charity car-boot sale.