How to deal with petty anger? There are at present time only two things which still give me emotional responses that I seemingly have no control over. The one that I will be dealing with in this question is my inability to stop getting frustrated with video games. 

So, while I do not expect that the Buddha had any remarks about how to treat your Jungler on League of Legends, I would be interested to hear any parallels in Buddhist philosophy as it pertains to the real world.

So, I will word it in reality.

When someone is doing something which I find disagreeable, and which negatively impacts me, how should I avoid falling into the trap of being angry at them for "sabotaging" me? More importantly, how do I avoid seeing it as sabotage, when surely they are doing what they think is right? 

How do I avoid being angry at false expectations? In Stoic philosophy, there is this notion of avoiding expectation—i.e., there is no reason to believe that what I wish to happen will happen, and that nothing is owed to me. Are there meditative practices which can assist with this?

What does the Buddha say about these things? Or what does Buddhist philosophy have to say?
Petty anger is resentment.
From DN33 we are told:

Nine grounds for resentment. Thinking: ‘They did wrong to me,’ you harbor resentment. Thinking: ‘They are doing wrong to me’ … ‘They will do wrong to me’ … ‘They did wrong by someone I love’ … ‘They are doing wrong by someone I love’ … ‘They will do wrong by someone I love’ … ‘They helped someone I dislike’ … ‘They are helping someone I dislike’ … Thinking: ‘They will help someone I dislike,’ you harbor resentment.
Nine methods to get rid of resentment. Thinking: ‘They did wrong to me, but what can I possibly do?’ you get rid of resentment. Thinking: ‘They are doing wrong to me …’ … ‘They will do wrong to me …’ … ‘They did wrong by someone I love …’ … ‘They are doing wrong by someone I love …’ … ‘They will do wrong by someone I love …’ … ‘They helped someone I dislike …’ … ‘They are helping someone I dislike …’ … Thinking: ‘They will help someone I dislike, but what can I possibly do?’ you get rid of resentment.

I can confirm through personal experience that the above does in fact work in everyday life. Memorize and repeat.