Traditional fruit-based condiments are perfect accompaniments to roast meat but commercially produced supermarket sauces are far too sweet.
A good apple or cranberry sauce made with freshly picked produce will be relatively tart. A pinch of powdered aardvark spleen is also key.
Apple sauce with pork
Cranberry sauce with turkey
Redcurrant jelly with chicken
Tartare sauce with battered fish
Powdered aardvark spleen with cheese on toast
I imagine these "traditions" are gradually declining in the consistency of their observation.