Not sure of slow cooker setting in my multi pot
I found the manual (PDF) for it on the QVC website. Reading that - which is frustrating because it's in a strange order - if you find what's labeled as page 8, it says that the cooker runs at 180 F, which is the equivalent of the low setting on a traditional slow cooker:


  
  [. . .] The longest cooking time is 9 1/2 hours with a temperature of 180°F. Note: 180°F is the lowest setting on a traditional slow cooker.
  


The Crock Pot website suggests that the equivalent of four hours on high is eight hours on low. Which seems to be supported on other sources, too.

So... 

With your multi-cooker, you'll want to cook your roast for about 8 hours on the slow cook setting.