Hi Omkar Khandare,
You Can use liferay's default UserAPI to get this.
The method which you are looking for is in com.liferay.portal.service.UserLocalServiceUtil
In UserLocalServiceUtil class you have a method named --> static List<User> getRoleUsers(long roleId);
It will return List<User>
For further reference you may visit following link
http://docs.liferay.com/portal/6.0/javadocs/com/liferay/portal/service/UserLocalServiceUtil.html
Signez svp dedans pour marquer ceci comme inadéquat.