Rock Lee has a lot of combos and strong attacks. He becomes stronger when he opens the Gates of Life. Try to dodge as much of his attacks as possible, or keep him at distance with long range attacks or your special technique. It may also be wise to not let him use his special technique; the more Gates of Life he opens, the more powerful he becomes and soon his Primary Lotus will become a Hidden Lotus. However you can take advantage of that and attack Rock Lee when he is done using his Hidden Lotus because his health will be very low. Make sure you also have enough Chakra and health remaining.