Cooking turkey joints
I guess you are talking about a pre-seasoned convenience product in an oven bag like this Butterball Ready to Roast boneless skinless turkey breast?

Well, the website writes:


  Ingredients
  Boneless Turkey Breast. Contains up to 25% of a solution of Water, contains 2% or less of Salt, Sugar, and Sodium Phosphate to enhance tenderness and juiciness.


This is like a super-brined piece of meat that consists of 3/4 meat and 1/4 watery brine. You don't want to thaw that because during thawing you'd likely lose a lot if the additional liquid. In the oven, the product thaws and the additional water keeps the meat moist, the sealed bag contributes to this.

It's imho not a classic roast (different ingredients, different preparation method), for an untreated turkey breast the "defrost first" rule is still valid.