Place lamb roast directly into bottom of slow cooker
Combine butter, rosemary, garlic, salt and pepper and mix well to form the herbed butter
Use a spoon to spread the butter over the top and sides of the lamb.
Combine wine, stock, paste and water and stir well to mix.
Pour this liquid into the bottom of your slow cooker around the lamb (but not down over the butter)
Baste meat with cooking juices during cooking occasionally if you are around to do so.
Cooked on HIGH for 5hrs in my 5L Breville Slow Cooker
Just before serving I removed lamb from slow cooker then scooped out excess fat from top of the sauce in the slow cooker (lamb being very oily you will be able to scoop a lot out)
Then I combined the cornflour with a spoonful of tap water and stirred through juices and placed the searing slow cooker on a stove top to reduce the liquids into a lush gravy for the lamb. If your slow cooker isn't a searing model just transfer sauces to a saucepan on stove to do this step