For Externally Procured Materials (ex - ROH) - SG's are maintained or not?

Hello

Do I need to maintain SG's ( like SG10, 40, 70) for ROH as these are externally procured?

As I see since ROH are externally procured, no need to maintain the SG (10, 40, 70,etc) in MRP 3 view of the ROH* material master as SG's (10, 40, 70)* are meant for maintianing PIRS & PIRs means it is inhouse production

Iam not limiting myself to SG's (10,40, 70) for ROH, instead any SG need not be maintained for ROH (externally procured)

If I want to see that ROH materials get consumed by the FERT then maintain SG 40/70 for the FERT/HALB (inhouse production) that should consume the ROH (externally procured)

Questions:

Q.For externally procured materials do I need to maintain the SG?

Q. If no need to maintain SG's for externally procured materials then what fields do I need to maintain to see that externally procured material which are used in the finished product gets consumed by sales orders?

Please clarify

Thank You