Roam alone ... push through the awkward phase to enjoy a party on your own.
From Sunday Life
So you've been invited to a soirée and your usual back-up - spouse, friend or co-worker - either can't make it or isn't invited. It's tempting to cancel at the last minute, or submerge your social anxiety in booze. But there is the risk with the latter that you'll end up doing something you'll regret, and while vomiting in the host's bathtub, for example, is easily cleaned up, the social stain left behind may be a tad more difficult to live with - especially if that's where they kept the beer.
If you're not terribly close to the host and it's not a sit-down affair, you can arrive late; that way, the party will already be in full swing. Don't begin at the food table as this is the habitat of socially anxious people and you'll be setting yourself up for an awkward evening.
If your host is gracious, they will introduce you to someone, but if not, grab a drink and locate the nearest nest of people. Introduce yourself and ask everyone how they know the host. A friend of a friend once told me this and it's helped enormously: accept that the first two minutes will be awkward. You're all strangers or acquaintances, so why wouldn't it be? Just push through until you're chatting away.
If there's no chemistry, excuse yourself by saying you need a refill, go to the bathroom, tell your reflection it looks amazing and get back out there. If you strike out again, you can always wander back to the food area where some poor, awkward introvert will be only too happy for you to strike up a conversation.