Competitive Roamer and Babysitter Roles?

Recently I have been very interested in competitive Roamer and babysitter heroes.
Roamers who dont stay in lane instead they jump from lane to lane ganking or assisting in ganks!
Babysitters who require little exp and help protecting your lane's carry!

Which are the best roamer and babysitter in the game in your opinion and state your reasons?

Vengeful Spirit = Best roamer?
Shadow Priest = Best babysitter?

Vengeful or Sven, IMO are the best roamers whereas Crystal Maiden and Earthshaker are the best babysitters.

Imo Ancient Apparition and Enigma are also among the best babysitters.

Ancient Apparition:-
... AA's "Cold Feet" can disrupt the opponents farm pretty well.
... His "Ice Vortex" can intensify the amount of magic damage opponents receives.
... Very item independent.

Enigma:-
... "Demonic Conversion" can serve multiple purposes - to deny creeps, to harass or simply to earn extra gold while babysitting through jungling.
... "Malefice" (is the most irritating stun in the game imo) which opens up possibilities of kills.
... Somewhat item independent.

As for roamers, I agree that Vengeful Spirit may be the best roamer.