This post will give some SQL Quires that support subject.

Here is my human task and I need to get role for connected to those task process.

Need user name for each task instances in wso2 BPS.

SELECT ORG_ENTITY_NAME "User Name", TASK_ID "Task ID"
FROM HT_GENERIC_HUMAN_ROLE ghr, HT_HUMANROLE_ORGENTITY map, HT_ORG_ENTITY org
WHERE ghr.GHR_ID = map.HUMANROLE_ID
AND map.ORGENTITY_ID = org.ORG_ENTITY_ID
AND ORG_ENTITY_TYPE = 'USER'

Need task instances per user

select TASK_ID  "Tak ID"
from HT_GENERIC_HUMAN_ROLE ghr, HT_HUMANROLE_ORGENTITY map, HT_ORG_ENTITY org
where ghr.GHR_ID  = map.HUMANROLE_ID and map.ORGENTITY_ID = org.ORG_ENTITY_ID
and ORG_ENTITY_NAME="regionalClerkUser"

Need to get the POTENTIAL_OWNERS, BUSINESS_ADMINISTRATORS and ACTUAL_OWNER for particular task instances.

SELECT ORG_ENTITY_NAME "User Name", GHR_TYPE "Organization Entity"
FROM HT_GENERIC_HUMAN_ROLE ghr, HT_HUMANROLE_ORGENTITY map, HT_ORG_ENTITY org
WHERE ghr.GHR_ID = map.HUMANROLE_ID
AND map.ORGENTITY_ID = org.ORG_ENTITY_ID
AND TASK_ID =351

Build services with  above queries and enjoy more details with WSO2 BPS Human task and users/ roles