Hi Robin,
First of all, sorry it took me so long to chime in on one of your threads, and a very big welcome to YLF from me as well:-)
I personally don't think rolling trousers or jeans always makes a look more casual. It also depends on the type of footwear you are sporting, and the rest of the outfit. E.g. a pair of slim-fit boyfriend jeans or dressier trousers with tapered hem paired with a pointy toe ankle strap pump, button-down shirt or silky blouse, and a fun blazer will read a lot dressier than e.g. rolled slouchy boyfriend jeans with a T-shirt and sneakers.
I use a different "number of rolls" depending on the bottoms and footwear. e.g. two rolls on my slim-fit boyfriend jeans when I wear them with ankle boots so that the entire top of the bootie is exposed and there is maybe a sliver of skin between the boots and the jeans.
When wearing tapered trousers with ankle strap pumps or sandals, I would roll the trousers until they showcase the ankle strap of the shoe.