Hi Kewin, although men do use 俺 it can be considered quite rude as it is quite a direct way of saying "I". It tends to only be heard in アニメ or when a male is displaying a lot of confidence with his male friends at a 飲み会 or other such meeting. Men tend to use the personal pronoun 僕（ぼく）in daily speech. In regards to the second question, Japanese keeps personal pronoun genders neutral like "私たち" can be used by both male and female, it doesn't matter about the gender. ーたち is actually quite different from English as it can also mean "Them". For example you can say "マイクたちはコンビニに行きます" Literally meaning "Mike and the group will go to the convenience store". You'll get the hang of it eventually after of practice and exposure to the word.