Is round ticket needed to apply for visa?

I work for an international company that has an office in Shanghai.
My travel dates are not fixed yet, but it will be definitely in the range of 1 week (November 27 and December the 3rd)
Is it possible to apply for a visa without the booked round ticket?
I have the invitation, application form and the license of the Shanghai office. Will that be enough to get an entry permit?

Thank you very much in advance.
Best regards,
Marharyta