Jay-Z is taking up a whopping 50 rooms for the lavish opening of the Cosmopolitan of Las Vegas. The star, who’s performing at the event along with Coldplay on New Year’s Eve, has “requested the rooms for his entourage and for his personal security,” a source told us. As a result, hotel managers have had to rearrange accommodations for other important guests. Celebs expected at the bash, produced by celebrity event designer Colin Cowie, include Jennifer Lopez, Marc Anthony, Alex Rodriguez, Mark Wahlberg, Kristin Davis, Ellen Pompeo, Kellan Lutz, Jamie-Lynn Sigler, Olivia Munn, Emmy Rossum, Jessica Szohr, Mark Salling and Selita Ebanks. Jay’s rep wouldn’t comment, but a hotel rep said, “We are looking forward to welcoming Jay-Z to the Cosmopolitan of Las Vegas, and as is our policy, we don’t disclose details regarding a guest’s accommodations or other arrangements while at the resort.”