RockYou has acquired Playdemic, the United Kingdom-based developer of farming-plus-cooking Facebook simulation game Gourmet Ranch. The plan, as RockYou’s new games product leader Jonathan Knight told us in an interview yesterday, is to turn Playdemic into the company’s second studio.

Gourmet Ranch, built by Playdemic’s team of game industry veterans, has been part of bumper crop of smaller but successful games that have emerged on Facebook over the past year (check out our review of it in August for game-play details). Today, the developer’s lone Facebook title has 540,000 monthly active users and around 100,000 daily active users on AppData — numbers that suggest it has been monetizing well.

RockYou’s first studio is at its Redwood City headquarters — while the company has developed a wide range of apps over the years, as well as its own ad network, the focus is now on social gaming.

It launched its first true social simulation game, Zoo World, back in 2009, and has [updated: not launched any major games since other ones, like Farm Land and Toy Land, have not fared nearly as well.] It’s been busy nurturing its main game, though, and after a number of rises and falls in the past year the app is bringing in nearly 9 million monthly active users and 1.25 million daily active users as of today, according to our AppData measurement service.

It also quietly bought TirNua, a small company that was building a virtual world, at the beginning of December, and it has moved the company’s technical team over to technical leadership position for Zoo World and other social games, according to Knight, also a recently-hired veteran game industry producer.

Playdemic’s 16 employees will join RockYou’s existing workforce to total 170 people (it’s down significantly  following a massive round of layoffs this past fall). That number, however, doesn’t include the RockYou Asia branch of the company that publishes games on Asia-based social networks.

While RockYou was at the fore of social app development over the past decade, and still has large non-gaming apps like Birthday Cards (which lets you play Zoo World inside of it) and Pieces of Flair, it has been passed in size and revenue by Zynga, Playdom, Playfish and other developers over the last couple of years. Today, including Playdemic, it’s the 12th largest developer on Facebook, with nearly 20 million monthly active users and 1.25 million daily active users, according to AppData. The company has also raised multiple rounds of funding adding up to around $130 million.

So between its strong foothold in social games, its new acquisitions, and