And my roots are a light brown and the rest of my hair stayed brown.
I was told by a girl working at a sally beauty supply that I should dye my hair light ash blond
(I want blond hair) and all my hair would get lighter.
I still want to go blond but I don't know if I should bleach it or dye it or what.
Any advice?

I'm guessing your natural hair colour is sumwhere around med brown?

Well your roots only turned out light brown... hmm well if the current colour on your hair is not natural it is impossible 2 lift colour with colour so I would recommend a dye remover {"colour opps" works wonderfully} if the colour on your hair is darker then your natural colour...

But I f this is all your natural colour then you would unfoutanitly have 2 bleach it which is vry harsh and quit unpredictable

If your natural color is brown a hair color from Sally's is not strong enough to go Blond. Even a highlift color with 40 vol wouldn't be strong enough to pull a nice blond and I wouldn't recommend doing it yourself . If you came in to my salon I would recommend
That you start highlighting your hair with bleach. After about 3 or 4 highlights your hair should be pretty blond. I never do recommend someone put bleach all over. The upkept is a lot and it usually looks very unnatural.:)