UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF THE

SECURITIES EXCHANGE ACT OF 1934

December 5, 2012

Date of report (Date of earliest event reported)

ROADRUNNER TRANSPORTATION SYSTEMS, INC.

(Exact Name of Registrant as Specified in Charter)

4900 S. PENNSYLVANIA AVE.

CUDAHY, WISCONSIN 53110

(Address of Principal Executive Offices) (Zip Code)

(414) 615-1500

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

On December 6, 2012, we entered into an Underwriting Agreement (the “Underwriting Agreement”) with Robert W. Baird & Co. Incorporated, as representative of the several underwriters named in Schedule I thereto, for the issuance and sale in a public offering of 3,500,000 shares of our common stock at a public offering price of $17.25 per share, less an underwriting discount of $0.9919 per share. We are selling 3,400,000 shares in the offering and a selling stockholder is selling 100,000 shares in the offering. Under the terms of the Underwriting Agreement, we have granted the underwriters an option to purchase up to 525,000 additional shares at the public offering price less the underwriting discount to cover any over-allotments.

Assuming no exercise of the underwriters’ over-allotment option, we expect to receive net proceeds from the offering of approximately $54.9 million after deducting the underwriting discount and estimated expenses of the offering. We expect to use the net proceeds from the offering to repay the outstanding indebtedness under our revolving line of credit and for working capital and other general corporate purposes.

The offering is being made pursuant to our effective Registration Statement on Form S-3 (Registration No. 333-176225), as amended (the “Registration Statement”), as supplemented by a preliminary prospectus supplement dated December 5, 2012 and a final prospectus supplement dated December 6, 2012.

The Underwriting Agreement contains customary representations, warranties, and covenants that are valid as among the parties as of the dates set forth in the Underwriting Agreement, and are not factual information to investors about our company. We expect to close the sale of the common stock on December 11, 2012, subject to customary closing conditions.

The foregoing summary of the Underwriting Agreement is qualified in its entirety by reference to the actual Underwriting Agreement, which is filed as Exhibit 1.1 hereto.

In connection with the offering and sale of the common stock, the following exhibits are being filed with this Current Report on Form 8-K to be incorporated by reference into the Registration Statement: (i) the Underwriting Agreement (Exhibit 1.1), (ii) the opinion of Greenberg Traurig, LLP as to the legality of the shares of common stock (Exhibit 5.1), and (iii) the consent of Greenberg Traurig, LLP (Exhibit 23.1).

On December 5, 2012, we issued a press release announcing that we had commenced the offering described above in Item 1.01 of this Current Report on Form 8-K. On December 6, 2012, we issued a press release announcing that we had priced the offering described above in Item 1.01 of this Current Report on Form 8-K. A copy of the press releases are filed as Exhibits 99.1 and 99.2 hereto.

Not applicable.

Not applicable.

Not applicable.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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