The 23-year-old, who can play wide or as a striker, joins on a two-year contract from Billericay Town after impressing on trial.
Toyosi began his career with Wimbledon, scoring on his debut, and has had trials with Chelsea and Wolverhampton Wanderers.
But it is Boro who have taken the plunge.
"I wanted to give him an opportunity," said Warnock.
"I came from non-league myself, I watched him play and I just had hunch. He knows Isaiah (Jones) too, which is a plus.
"I hope he enjoys himself here, it's a big ask but I hope he can excite everyone here like he excites me. He's got a great attitude."