Detective Superintendent Vicky Tunstall of Central East Command Unit said: "We understand that the increased police presence in Hackney this week will be concerning for residents.
Detective Superintendent Kelly Allen, from Specialist Crime North, said: "This investigation has moved quickly with officers arresting four men within five days.
Jason Junior Romeo, 20, was fatally stabbed outside an address on Bodney Road in Hackney following an altercation at about 6pm on Tuesday, police said.
Mr Roberts has links with Hackney and Dagenham, the Metropolitan Police said, but it warned members of the public not to approach him and instead call 999.
They are Raynolph Asante, 22, of Pembury Road, Travis Mitchell, 21, of Bodney Road, and Rhamyah Bailey-Edwards, 21, of Williams Avenue in Walthamstow.
