What champs should i play in ranked(solo)?

Ive been climbing the ranks pretty fast recently while playing team champs like malphite and rammus in duo que. But when i try to solo using these champs i feel like people can never follow up and i just end up losing. Should i be using carry champs in the mid/top lane instead? Im pretty good at fizz but i feel like if i dont pick that tanky engage, no one will. So basically whats your opinion on the situation, should i switch champs? And what champ should i play?