Police are appealing for any members of the public to make contact if they were in their vehicles in the vicinity of Trevethick Grove, Whites Line West, and Ludlam Crescent at the time, and have dashcam footage.
Staff are continuing their inquiries at the crime scene today, speaking to people who live in the area as well as partygoers at a Trevethick Grove address on Friday night.
Initial inquiries indicate the men had attended the party before they were assaulted, according to an earlier police statement.
"We are also urging residents of this area to check their properties for any items that do not belong to them and that may have been involved in this offending," police said.
People with information or footage are asked to contact the investigation team on 105 quoting 211218/4047.
Information can also be passed on anonymously by contacting Crime Stoppers on 0800 555 111.