When I buy sausages I ALWAYS cook first then freeze. I then reheat in the microwave. I do it with beef burgers too. I don’t think there’s much that I don’t cook first then freeze. Never had any problems.
I have made my own pigs in blankets, put in disposable tin trays, covered in foil, and in the freezer. Also made sage & onion stuffing, and sausage meat balls. In freezer the same. Get them out, night before you need them, then straight in the oven, on day, to cook..cheeper than buying them ready done.
If they are raw Fresh or Frozen then yes you can. Rule of thumb is Fresh Raw, Freeze, Defrost, Cook, Refreeze. De frost, heat up to piping hot and eat. Do Not Re freeze. Then you have Cooked, Freeze, Defrost, Re heat to piping hot. DO NOT Re Freeze.