''Roaming is easier said than its done tho.
More often than not its just not worth, youre gonna maybe lose a tower, your team is dead/ ''
You need alot of practice in timing Aggression, also once you get good at it, losing tower wont be a Issue, because you will take much much more in exchange and If you are Truly strong, you can still take his Tower when you return and ''Losing'' your lane is less likely if you are a Good player instead you worry about the other lanes because they infinitely are mostly worst.. but in general you plan ahead, as in Kill mid and then Push bot, etc.. just a simple example
Being good at Roaming takes skill and Lots of practice in normals, you don't just get Good at it, you need to do it alot and then it becomes second nature.
''your team is dead/ too low already anyway, your enemies are so fed, they would probably just kill you too,...''
Example of a Bad roamer.. he does things after everyone is far behind.. ''Roaming'' is done really early, the faster the better, if you let lanes get trashed then your not a good ''baby'' sitter.. usually you Co-ordinate with the Jungler, if you are a Laner and Hope to get a 4 vs 2 or 3 vs 1 scenario to get back into the game.. Inshort you don't just let things slide into oblivion. communicate alot with your Jungler.. if you are the Jungler make sure to Free up mid and ask him to Gank bot with you for a 4 vs 2.
''But a lot of times the situation isnt good. I have to way the cost of teleing bot to save the adc and lose top, or hope the adc can survive by themselves and save top.''
You do not Teleport to save anyone.. YOu teleport to make plays and Take the Drake and maybe even a Tower.. If your mentality is to defend, then you will lose all your games.. Mentality should be to TP in first while talking to Jungler to come etc.
league is a Numbers game, Once you trash Bot with more people.. YOu take drake + Tower etc.. now your team is ahead in Gold..
You then Roam mid Same story.. You then keep trashing everywhere..
Meanwhile that other Player on your lane has minimal impact on the map
Okay so that other Guy took Top tower.. So what ?? 5 minutes later you take his tower.. nothing has been gained.. except You took a Dragon + Tower and Now also put Botlane in better situation.. Meanwhile Top took a tower he would have taken anyway.. Since its not a Inner tower.. it matters very little..
You must understand Value.. your ''Map'' Presence is what creates victory.. a Player that influences many sides of the map Carries teams.. not a Player that Protects one Tower top.. How much value is that top tower ? Not much in comparison in Putting bot ahead and Taking Bot tower and taking a Drake.. I would say its a great trade.
League is a Team game.. you shoudl be able to Defend top even After being set slightly behind.. if you can't then you are too weak to carry.. I set myself behind in order to babysit other lanes, because i Know i can still do really good despite a Slight disadvantage from Roaming, While i expect my team to not even Win their lanes with advantage.. so do remember You win League by carrying the worst, not by Winning over the best.
Its that simple.