What is the Dawes Roll, and who was registered on it?
Congressman Henry Dawes was a big advocate of property ownership and he asserted that it was a necessary component of civilized life. The rest of Congress agreed, and in 1887 they enacted into law the Dawes Act. The Act stated that the United States government would provide for the allotment of lands in Indian Reservations. The Cherokee Nation was divided into thousands of small pieces of land, which would be distributed among the Cherokee people. On the surface the act was an attempt to assimilate the Native people into white society, in itself a less than admirable cause, but in reality the Dawes Act did far more than Anglicize the Native Americans. The Act allowed for widespread fraud by government officials and legally stripped Native Americans of much of their land by allowing land not allotted to be opened to settlers. The Dawes Roll was the official roll of the Dawes Act and was open from 1899-1906. In order to receive a parcel of land Cherokees had to sign the rolls. In order to sign the rolls a Cherokee had to have a permanent residence in the Cherokee Nation and have appeared on previous rolls. Those who signed the Dawes Roll provided their names and blood quantum and in return were granted a piece of land in the location they desired. In addition to the "Cherokee by Blood" portion of the Dawes Rolls, there were separate rolls for Cherokee Freedman and Intermarried whites living in the Cherokee Nation. 

My ancestors are on the Dawes Roll and I have their roll number. Now what do I do?
If you have the roll number you're half way there. All you need in order to apply for a CDIB card are acceptable legal documents that connect you to an ancestor who is listed with a roll number and blood degree on the Dawes Roll and your birth certificate. Once you have submitted this information they will approve or deny your claim. If your claim is approved you will receive your CDIB (white card). Now you are eligible to apply for membership to the Cherokee Nation (which comes in the form of a blue card). Descendants of Freedman cannot receive a CDIB, because the Freedman roll did not include quantum calculation, but they are eligible for membership in the Cherokee Nation as a descendant of a Dawes Roll signer.

For more information see: http://www.allthingscherokee.com/atc_sub_gene_feat_121100.html