What rolls mean

1-49 Future Haki and as the story goes on can progress to adv. Future haki and minor Armament haki

50-99 Armament haki and as you grow you can learn Advanced Armament Haki also being able to learn minor future haki

100 Conqurers Haki as well as the ability to major both other kinds of haki.

For those curious advanced Haki is using it in a way unique to your character.
For example someone who has eaten the Ice Logia can manifest freezing Haki
Or someone whos very hot headed or passionate can Ignite their armament Haki.

those who are very particular about cirtain things can use their future haki to predict very specific things such as weather or mental attacks.