I'm no expert but I would very much suspect worms if I found something long and whitish in sheep poo.
Your 'tagliatelle' and 'rice' description fits tapeworm- either a whole worm (tagliatelle) or segments (rice) which is common with tapeworms being excreted.
If you search for 'tapeworm sheep dung' and check the 'images' section you will find quite a few quite graphic images you could compare with what you found. As far as I am aware (and just confirmed by shep53 crossposting) tapeworms are not harmful to sheep, but if in any doubt take a poo sample to your vet.