In your portlet's code you can use below method as defined in portlet specification:
portletRequest.isUserInRole("roleName");
Note: Liferay doesn't use the isUserInRole() method in any of the portlets provided by default. Instead it uses Liferay's permission System directly, to achieve more finegrained security.
For more information please refer to below Link
https://www.liferay.com/documentation/liferay-portal/6.1/development/-/ai/security-and-permissio-4
you can use some method which are there in PermissionChecker.
ThemeDisplay themeDisplay = (ThemeDisplay)request.getAttribute(WebKeys.THEME_DISPLAY);
PermissionChecker permissionChecker = themeDisplay.getPermissionChecker();
permissionChecker.isCompanyAdmin() // Returns true if the user is an administrator of their company.
permissionChecker.isOmniadmin() // Returns true if the user is a universal administrator.
permissionChecker.isGroupAdmin(long groupId) // Returns true if the user is an administrator of the group.
for more information about PermissionChecker please refer to below link http://docs.liferay.com/portal/6.1/javadocs/com/liferay/portal/security/permission/PermissionChecker.html
you can also explore RoleLocalServiceUtil
class of Liferay
http://docs.liferay.com/portal/6.1/javadocs/com/liferay/portal/service/RoleLocalServiceUtil.html