Roku and Chromecast come with 4K now, but you don't need them yet

It’s the holiday season, which means millions of people are leaving stores with a new 4K Ultra HD TV. Google and Roku are hoping that they’ll also tack something else onto that big purchase: a streaming gadget. Both companies have recently released products that can play stunning 4K (and HDR) videos from popular streaming services.In the case of Roku, you’ve actually got several new devices to choose from, led by the top-of-the-line $130 Roku Ultra. And Google has expanded the