Sunny you dont need to roast the whole goose now.. just the legs.. freeze the breasts raw and use them on the day ..
stock : put all the rest of the carcass raw or cooked ) in big pot, add one onion halved , stick of celery ( and celery tops if you have them) a carrot ( dont need to peel it. about 10 peppercorns, and a sprig of thyme if you have it.
Cover with water ...bring to boil , turn down to a slow 'plip' ...lid on so water doesn't boil away .. Plip for a hour or so....
if there is a lot of fat - which there will be with a goose - just carefully spoon off as much as you can into a jug after about an hour of cooking ( dont throw this away its great for spuds!!) . Don't worry too much if you cant get much out ..but it is easier if you can a bit..
Once its cooked for about 90mins turn off heat , leave over night covered ... ( if yo have a cold place like a conservatory or garage at this time of year even better because the fat will solidify .
In the morning carefully remove as much fat as poss ( keep this also - I put it into a jar in the fridge for roasties).
Heat it all up again a very little just to make stock liquid again , strain through colander into a bowl. Discard bones ( but if there is any meat left on carcass strip it off and either save for soup ,give to dog (or eat!)
If you have a fat strainer jug now is the time to use that (really good to get one of you are making stock) .. strain off fat pour back de-fatted stock into cleaned pan , and boil vigorously to reduce and concentrate..
I then pour it into ice cube trays and put n freezer..
Yes it s a faff, but . I only buy one local chicken (quite £) once a month maybe and that's how I Mumsnet the hell out of it!