Hi, Salman!
Different customers use different approaches. It depends on internal security policy.If customer has obligatory requirements for SAP roles (restrict/regroup/rename), you have to follow them. If customer do not specify requirements for SAP roles it would be better to use standard roles copied to Z.
Yes, you have to create business partners and users in SAP Solution Manager for all end users who will create support tickets. Use transaction BP_USER_GEN for this.
Andrey