Shen
Designed with his ultimate ability in mid, Shen is a support top lane champion who has incredible roaming potential. His ultimate allows him to shield any ally on the map, and teleport him to their location.
Usually played with teleport, since lane kills are not something Shen focuses on, this champion can easily teleport across the map with his ultimate, and then teleport back in time to catch his minion wave. Due to this, he is one of the best champions to roam with from the top lane.
During the late game, it becomes a useful tool to split push in a side lane, knowing you can always join your team in the case of a team fight.
Pantheon
The Spartan of League of Legends is a fighter whose abilities allow him to establish an easy early-game dominance in lane, allowing him to crash the minion wave into the enemy turret, and roam across the map.
Of course, roaming is made easy for Pantheon due to his ultimate, which allows him to jump halfway across the map, to join a team fight or a skirmish for objectives against the enemy jungler.
Quinn
Few champions are designed to be ranged top laners in League of Legends, but Quinn is one of those! Due to this, her laning phase consists of bullying the enemy, and forcing them to farm under their own turret, allowing Quinn to roam freely.
With her trusty falcon carrying her as her ultimate, her movement speed skyrockets, allowing her to move to the mid-lane as quickly as if someone teleported there!
Kled
The hillbilly of Noxus, Kled is a Yordle who rides on an immortal mount. and that mount, coupled with Kled's spurring, charges with great speed at an enemy they locked on, and also serves as an excellent engage to team fights!
In addition to that, the ult speeds up Kled's entire team as well, if in range, making Kled a top lane champion with great jungle synergy with any jungler, for easy ganks to the mid lane, and even bot lane if need be!
Sion
Following the theme of ultimate abilities that allow champions to cross great distances, Sion's ultimate makes him into an unstoppable juggernaut that flattens everything in his path at great speed.
With his ultimate, whose duration allows Sion to cross half of the Summoner's Rift, Sion can easily roam and gank an enemy champion during the mid-game, and transition to using it for split pushing during the late game.
Warwick
Unlike the easy to learn beginner jungle champion that Warwick is, his top lane playstyle focuses on his incredible sustain and healing, to achieve an early game advantage in lane.
This is done by playing Wawrick with the Barrier Summoner Spell and building omnivamp items, to increase Warwick's healing.
Playing Warwick this way, allows him to make full use of his W ability, which gives Warwick bonus movement speed when scenting a low-health enemy champion. With a laner that is too behind in gold to follow, Warwick roams easily, establishing complete map dominance for his team.
Akshan
As a typical ranged top lane champion, Akshan establishes a powerful prio in lane, due to his ranged auto attacks. By doing so, he frees himself up to play with his jungle and roam around the map.
Clever use of his E ability allows Akshan to use walls as aids in moving quickly across the map, instead of them being obstacles, while his W grants him full invisibility, making every roam a successful gank easily, as enemies won't know what hit them!
Camille
While it may not seem like it, Camille is actually quite an effective top-lane roaming champion! This is because her E ability allows her to jump over walls and roam to other lanes quickly.
Coupled with an ultimate that locks down a single enemy champion, preventing them from escaping, whenever Camille leaves her lane for a gank, it will result in a kill!
Tryndamere
Tryndamere's entire playstyle relies on pushing his advantage with his early crit chance, and superb wave management to both deny the enemy team their own resources while improving the cs farming in LoL, as much as possible.
It all culminates with Tryndamere abusing his short-cooldown E, a short dash that can go through walls, and roam across the map, both to steal jungle camps and ganks enemies.
With a good jungler to play with, the enemy will never be able to take a neutral objective, while a good mid-laner means that Tryndamere's ultimate can be used to dive the enemy as early as level 6.
Akali
Roaming is usually the dominion of mid-lane assassin champions. And Akali is the only assassin in League of Legends who can, reliably, be played in the top lane regardless of the meta!
Her kit allows her to go toe-to-toe with even the best top lane champions in LoL, while also fulfilling the niche of one-shotting the enemy ADC and living to tell the tale.
With multiple dashes that can go over obstacles and insane amounts of magic damage, Akali's roams easily transition into ganks!