Are they not all ministering spirits sent forth to minister for those who will inherit salvation?
Angels are servants of the King (God the creator) who serve those who will inherit salvation. Salvation here is not justification because it is in the future, not in the past. The reference is to believers or Kingdom Citizens who inherit the kingdom or rule in God's Kingdom as a reward for their obedience and service to the Son.
Constitutional Scripture: Hebrews 9:28
So Christ was offered once to bear the sins of many. To those who eagerly wait for Him, He will appear a second time, apart from sin, for salvation.
Constitutional Scripture: Colossians 3:23-24
And whatever you do, do it heartily, as to the Lord and not to men, 24) knowing that from the Lord you will receive the reward of the inheritance, for you serve the Lord Christ.
The author here is speaking about "the world to come"
Constitutional Scripture: Hebrews 2:5
For He has not put the world to come, of which we speak, in subjection to angels.
Constitutional Scripture in Reference to Salvation: Hebrews 2:3
How shall we escape if we neglect so great a salvation, which at the first began to be spoken by the Lord, and was confirmed to us by those who heard Him
Constitutional Reference Scripture: Hebrews 2:10
For it was fitting for Him, for whom are all things, in bringing many sons to glory, to make the captain of their salvation perfect through suffering.
Constitutional Reference Scripture: Hebrews 5:9
And having been perfected, He became the author of eternal salvation to all who obey Him.
Constitutional Reference Scripture: Hebrews 6:9
But, beloved, we are confident of better things concerning you; yes, things that accompany salvation, though we speak in this manner.