At the risk of sounding like Jerry Seinfeld performing a stand-up comedy routine, it still has to be asked: What’s with all these sushi places offering half-off sushi rolls? Sure, it’s incredibly convenient that something is permanently 50 percent off and you get double the sushi for your dough, but you’re also always left with a head-math problem every time you order. Anyway, with the growing popularity of this marketing gimmick, there are a few standout rolls I’ve encountered at half-price. These include the Spicy Johny and the Lucky 7 rolls from Arigato Sushi (1608 Howe Avenue and 1136 Galleria Boulevard in Roseville, www.arigato-sushi.com), the Crunch Monkey and the Lion King rolls from Sushi Hook (807 Howe Avenue, www.sushihook.com); and the Thunder Fire and El Camino rolls at O Bento Teriyaki & Sushi Roll (4128 El Camino Avenue, Suite 2; www.obentorestaurant.com). Caution: The Spicy Johny and the Thunder Fire are particularly spicy.