Advice

If you really love it the way it is, with brown lowlites, you need to go to a salon so someone can stand behind your hair and do a good job getting your highlights just where you need them on your roots. It's too difficult to do it at home when you can't properly see the back of your head, and it would be even more difficult to do a highlighting job where you're trying to avoid getting it on some of your hair (because if you want to keep brown lowlites, you don't want to just dye your roots blonde. You're right, it would look strange with blonde roots on brown hair).