The short answer is yes, you can. The longer answer is Swedish meatballs are different from Italian meatballs which are the ones we normally find frozen in the grocery store. You can use them, but the flavors will be different. You will also need to make the roux with 4 Tbsp of butter and 4 Tbsp of flour since there isn't any need to brown the frozen meatballs. After making the roux and deglazing the pot with liquid, add in the frozen meatballs and continue on with the recipe. The pressure cook time will stay the same.