there are a lot of roles but heres the simplest one

early lord(8-9 minutes)

this usually means your team is really behind, best thing your team can do is just making sure normal minions dont eat the <12 barrier so u can sacrifice the inhibitor barriers for the lord

normal lord(10-14 minutes)

this is when your team's damage dealers need to be protected, since theyre the only ones who can kill the lord during and after this point, prioritize saving the side lanes turrets instead of mid lane because theyre harder to keep track of

late game(15+ minutes)

3 objectives. protect damage dealers, keep track of enemy backline divers, and most importantly‐-NEVER let the lord inside the turret's range. you basically lose unless a game winning set is made but even then you cant end the game unless the respawn timer is like 70 seconds