The other team did not appear until the battle was over.
Roland smeared his face with mud, made a few cuts in his clothes, and lay on a heap on the ground as if he was injured like everyone else, waiting for the rescue from the Martialist Association.
Although Ling had pressed the "speaking" button on the walkie talkie by accident, fortunately, the communication was not open to all the teams. Therefore, only Fei Yuhan had heard their conversation. As she had lost her consciousness, Roland could totally attribute this bizarre communication to Fei Yuhan's perturbed mind and convince her that it was simply her illusion due to her injuries.
As to why the monster vanished in thin air without leaving the slightest trace behind, Roland could simply claim that he had well passed out before this incident had occurred. But by doing so, he could only ascribe the victory entirely to the genius girl, Fei Yuhan, and washed his hands off the whole matter.