Even after you take the turret should you continue to pressure lane or is roaming a must?
Lane phase is a part of the game to help people understand the mechanics.
When do a leave my lane ?
You can start roaming even before break the turret.
When is a good moment to start my roaming?
You start your roaming when:
- You have vision of the path you are going to (to avoid ganks)
- Your lane is pushed
- The opponent is not pushing your lane too hard
- After a kill and with good health, mana and cd
How can I do a good roaming ?
- Buy some wards to river.
- Be aware of the opponent wards.
- Don't let they know where you are or where you are going
- Keep good hit points, mana and cd
- Know where you have the major possibility of get the kill/help your team
When do I need stay in my lane?
- If your lane is in balance. (minions on the mid of the lane)
- If your opponent keep pushing (if you kill him, then is a good moment to roaming before recalling)
- If you are losing your lane
Completely depends on the champion you are playing and who you are laning against. Sometimes it is important for you to keep farming, especially if you don't have much of an ability to do roaming ganks unless of course your other lanes are losing and need help. Also, if you are laning against somebody who needs farm like Nasus for example, then you should keep denying them as much as possible. This is a very situational question.
These generic questions are impossible to answer. It depends on your team and how you like to play the game. If your team is ok with it and the role you play is that of a split pusher, then you never really leave the laning phase. A good example of this was HotshotGG of CLG.NA when he played his Nidalee. He goes solo top, and pushes all day. His team might give up dragon, but he'd be pushing to second tower on top. His team goes as 4 to pressure another lane, and he's still pushing top. He never really left top lane the whole game, so he never really ended the laning phase. This is a perfectly viable strategy if your team understands this and builds/picks for it.
Conversely, if you are Lanewick solo top, you know you have an amazing level 6 gank - since that's when jungle ww starts getting great ganks with his ult. So you may go ahead and choose to end the laning phase so you can start counterjungling, roaming, ganking, etc.
The one thing that can be said in a generic fashion is you should NEVER be idling in the game. If there are no objectives up and your team is not grouping to teamfight, then you should farm something, warding/counterwarding, do something. The only time you may idle is when your champion is going back to fountain or you just died and waiting for respawn timer.