Will i be charged at all for there mistake?

i had a apartment with a friend in lakewood that went through a ownership changing during our moveout. In November of 09 my roommate could not make his half of the monthly payment so i made it for him, same situation happened in dec of 09 than in january i was unable to pay his half so i only paid my half. Since my roommate couldnt pay i moved out and notified the office and they reported to me that i have to give them a two month notice which i figuered was out of the question seeing as how my roommate couldnt pay them. Before i moved out completly (only cleaning was left) we were evicted before the two months were up. Now two years later they have reported it to collectors and they have only contacted me. I have recieved a letter and notice my credit report was effected negativly. I have spoken to my old roommate and he has not recieved any notice and his credit score has not been effected.