俺 is very casual form which should be used among friends. This is used not only old men but also youngsters. 僕 sounds casual and should not be used in business. I recommend you to start from 私 to meet someone for the first time, 僕 after you become a friend with someone. 俺 should be used once you got at native level. If non-native spearker who has a smattering of Japanese uses 俺, it sounds very weird.

こんにちは，私の名前はイーサンです。（right） or こんにちは，イーサンです。 or 　こんにちは、イーサンと申します。（self introduction） (私) :for everyone (僕):usually for young boy (俺)：for old man

こんにちは，私の名前はイーサンです。（right） or 　こんにちは、イーサンと申します。（self introduction） (私) :for everyone (僕):usually for young boy (俺)：for old man