Hi Lotus, thank for your inquiry. We get this question a lot and we see the opportunity.
As of now, many of the B2B features available in OroCommerce such as requests a quote, submit proposal, multiple organizations, multiple catalogs, etc also serve the needs of a market place. We do not have all the capabilities needed (this obviously can vary form case to case) such as multiple vendors longing in to the admin consul and each managing its own catalogs and price lists etc. Saying that, this can be achieved with customization by a small team that has the technology skills. this customization should not be a heavy lifting but will require work pending your specific requirements.
As I said, we see a market place as a huge opportunity and the needed features are on our road-map
Do you have a project that you are working on? if so contact us directly https://www.orocommerce.com/contact-us so we could help