Roast turnip or cauli.
Low-carb gravy is easy. Take meat out of pan. Put pan on heat. Pour in liquid of choice (water, wheat free stock cube, wine) so the pan sizzles and the liquid immediately bubbles. It deglazes the pan of all the lovely burnt bits which is where the taste comes from. Ad anything you want to it, I used to put in the beef bits or chicken skin, herbs, salt, whatever you want and then leave it to simmer until it reduces. If you want a glaze, put a big knob of butter in at the end. If you want more gravy (reducing it concentrates the flavour but gives you less) thicken it with a bit of arrowroot or cornflower but be mindful off the carb rise.