Lost games as Omniknight Pos3 when stomping enemy lane - Hints please

Hey guys,

I've had yesterday game with Omni where I stomped bot with my supp (https://www.dotabuff.com/matches/8691545079). I started to roam when I was way ahead and helped my team, yet I feel like I started to do it to late.

Could you please hint me, what I've done wrong that we've lost this game? (I'm +/- Archont I).

I'm pretty much winning lanes with Omni every time, but I don't know how to carry the games using my lead :( Help me get better!