Not only you can random for any heroes in the pool, you can also random heroes according to their attack type (melee or ranged), primary attributes (intelligence, agility or strength) and role (carry, support, nuker, initiator, support etc.)
For eg, if you say "random melee carry nuker", it will random only melee carry nuker heroes.
As of now, it only takes up to 3 arguments at one time.