Not having something in writing makes proving your case tougher, but it is not necessarily fatal. The judge will look at whatever evidence you do have and try to determine whether there is sufficient evidence to show that you and your roommate had an agreement. That evidence does not always have to be a formal signed contract; it could consist of other writings that show there was an agreement.
Are there any writings or emails that at least show you requesting payment during the 14 months - or even better - ones with him responding that he will pay when able? Do you have any witnesses to conversations the two of you had about splitting costs? If you go to court, do you think the roommate will dispute that he owes you anything and instead claim that you allowed him to live with you free of charge? Have you made a formal written demand to him and requested a response in writing?
Without that sort of evidence, one big question/concern a judge may have is, if there was at least a verbal agreement from the beginning, how do you explain allowing someone to live with you rent and utility free for 14 months with no written assurance that you would ever be paid? The judge will be curious to know if there was some type of family or romantic relationship that could indicate that you never expected to be paid, but were fine letting him live there free. There are many other questions that can't readily be answered from your post, and there may be lots of additional information that may make a difference.
You certainly have the right to bring the case in small claims yourself. However, be forewarned: as the plaintiff bringing the lawsuit, you have the burden of proof. If it is simply your word against his, you will probably lose.
Normally, without an attorney to advise and/or represent them, folks without representation risk losing just because they don't know what evidence they need to prove their case, how to make sure that evidence will be properly admissible in court, etc. Therefore, I would suggest consulting with an attorney in your area that practices landlord-tenant law. He or she can advise you on your options and the the strength of your case in a much more in-depth manner than any website message board. While an attorney may charge you upfront, there is a chance you can get that money back if you win and your attorney successfully convinces the judge to order your roommate to pay your attorney fees and court costs.
Bottom line: if you are serious about getting your money back, your best option is to hire an attorney rather than handle it on your own.
DISCLAIMER: The above is intended for information purposes only and is not legal advice. Legal advice can only be given by an attorney following an informed consultation with a prospective client and a proper investigation of the facts and law that apply. If you are seeking legal advice, contact an attorney licensed to practice law in your area for a meeting.