The best way to heat frozen pies is to thaw them in the fridge from the freezer overnight then pre heat your oven to 360 F.
When oven reaches temperature:

Type of pie                                Cold                      Frozen

Individual pies                       20-30 mins             30-40 mins

Family pies                            35-45 mins             45-55 mins

Mini pies/Sausage rolls         15-20 mins              25-30 mins

Large sausage rolls             20-25 mins              30-35 mins

Microwaving will result in soggy pastry and is not recommended.

These times are a guide only, times may vary depending on the type and efficiency of your oven. Always reheat your pie to an internal temp of at least 65-75 C or 149-167 F knife or skewer should feel hot when plunged into center for 10 seconds.