In version 6.2.4 could be done but is not an automatic procedure should make as administrator level. Steps should be done are:
We will supose you want to rename ROLE_X to ROLE_Y
1- create role Y -> Administration / Roles / create role
2- execute in database query:
Code: Select allupdate OKM_USER_ROLE set UR_ROLE = 'ROLE_Y' where UR_ROLE = 'ROLE_X';
delete from OKM_ROLE where ROL_ID='ROLE_Y';
update OKM_NODE_ROLE_PERMISSION set NRP_ROLE='ROLE_Y' where NRP_ROLE='ROLE_X';
3- Go to Administration / Utilies / Rebuild indexes. Select lucene indexes and then click execute. ( That will propagate security in across search engine, can take several minutes, meanwhile is under execution repository will go to read only mode, do not worry, after process will be completed come back to normality ).
Tell us if has been solved your problem.