PrimeFaces 5.2 selectCheckboxMenu not support Map<String,String> style selectItems - primefaces

Question

I am trying to use
Map<String,String>
style selectItems in my
<p:selectCheckboxMenu>
but unfortunately, it not works.
Backing bean:
#Named(value = "roleBean")
#SessionScoped
public class RoleBean(){
private Map<String,String> roleMap;
private String[] selectRoles;
......
......
public void findRoleMap(){
if(roles.size()>0){
for(Role r:roles){
roleMap.put(r.getRoleId(),r.getRoleName());
}
logger.info("Role Map size: " + roleMap.size());
}
}
}
jsf as:
<p:selectCheckboxMenu id="roles" value="#{roleBean.selectRoles}" label="Select your roles" filter="true" filterMatchMode="startsWith" height="200" panelStyle="width:200px">
<f:selectItems value="#{roleBean.roleMap.entrySet}" var="entry" itemLabel="#{entry.value}" itemValue="#{entry.key}"/>
</p:selectCheckboxMenu>
When I access the page, I found there is 6 records were added into the map. but unfortunately, there is nothing shows up in the selectCheckboxMenu drop down list.
If I change the UIComponent to
<p:selectOneMenu>
from
<p:selectCheckboxMenu>
it shows up properly in dropdown list.
I tried to find out through google, I didn't find anyone else trying to use key/value pair in Map style as selectItems in selectCheckboxMenu. I was very confused.
My question is: Does selectCheckboxMenu support key/value pair mapping style or not, if it does. How To do it?
Please advise!!