Hi!
Good luck with your search for a job. I suspect that without a visa/residencia/work permit it's going to be v. difficult for you to obtain work.
One obvious thing to do is to find fellow Romanians and see if they have some contacts and what kind of work they do. There does seem to be a lot of people here who earn a living handing out leaflets at tube stations. I'm sure this is low-paid but cash-in-hand (not needing documentation). May be worth approaching the places that advertise in this way... If you do have the relevant documentation, may be worth going to Employment agencies such as Adecco..Sorry if this does not seem too helpful.
--The website
www.infojobs.net may yield more help?