SemGroup Corporation and Rose Rock Midstream Announce Planned Retirement of President and Chief Executive Officer Norman J.

SemGroup Corporation and Rose Rock Midstream Announce Planned Retirement of
President and Chief Executive Officer Norman J. Szydlowski

TULSA, Okla., Aug. 8, 2013 (GLOBE NEWSWIRE) -- SemGroup^® Corporation
(NYSE:SEMG) (SemGroup) and Rose Rock Midstream^®, L.P. (NYSE:RRMS) (Rose Rock
Midstream) today announced that Norman J. Szydlowski, who has served as the
company's chief executive officer since November 2009, will retire once a
successor is named and in place. Additionally, at that time, Szydlowski will
retire from his position as chief executive officer of Rose Rock Midstream. He
will continue to serve in his current capacities to ensure an orderly
transition.

SemGroup's board of directors has initiated a comprehensive search process to
identify a successor, considering both internal and external candidates. The
company has retained Russell Reynolds Associates, a leading executive
recruiting firm, to assist in the process, and Szydlowski will work with the
board to help identify his successor.

John F. Chlebowski Jr., chairman of the board of SemGroup, said, "On behalf of
the board and everyone at SemGroup, I want to thank Norm for his strong
leadership and countless contributions to our company. Among many other
notable accomplishments, Norm helped SemGroup establish a solid financial
foundation following the restructuring of SemGroup, L.P. and cultivated the
broad and talented management team that led the company through its successful
listing on the New York Stock Exchange in 2010. He also played a key role in
the launch of Rose Rock Midstream as a publicly traded MLP in 2011, and more
recently, in the initiation of a quarterly dividend to return capital to
SemGroup stockholders. In addition, SemGroup has continued to grow under
Norm's leadership, as evidenced by our recent acquisition of Mississippi Lime
gas gathering and processing assets from Chesapeake Energy Corporation, and
Rose Rock Midstream's recent announcement of an agreement to acquire
transportation assets from Barcas Field Services. We are pleased with
SemGroup's momentum and the strength of the company, and I am confident that
we will continue to build on our track record of growth, success, and
shareholder value creation."

Chlebowski added, "Norm's planned retirement is well-deserved, and his
willingness to continue in his current roles while the search process is
underway will help facilitate a seamless transition of leadership.I look
forward to working with him and the rest of the board to identify the right
successor to continue the success that the management team at SemGroup and
Rose Rock have accomplished."

Szydlowski stated, "Over the past several years, it has been my privilege to
work with the exceptionally talented and hard-working employees of SemGroup
and Rose Rock.Together, we have grown our business and strengthened our
position in the midstream industry, and I am extremely proud of all we have
accomplished.Working together, we have achieved my key objectives and today
both companies are well-positioned for more success, so I believe now is the
right time to transition to new leadership.I am confident that the board will
select an outstanding leader who will continue to grow SemGroup and Rose
Rock."

About SemGroup

Based in Tulsa, OK, SemGroup^® Corporation (NYSE:SEMG) is a publicly traded
midstream service company providing the energy industry the means to move
products from the wellhead to the wholesale marketplace. SemGroup provides
diversified services for end-users and consumers of crude oil, natural gas,
natural gas liquids, refined products and asphalt. Services include
purchasing, selling, processing, transporting, terminalling and storing
energy.

About Rose Rock Midstream

Rose Rock Midstream^®, L.P. (NYSE:RRMS) is a growth-oriented Delaware limited
partnership formed by SemGroup^® Corporation (NYSE:SEMG) to own, operate,
develop and acquire a diversified portfolio of midstream energy assets. Rose
Rock Midstream provides crude oil gathering, transportation, storage and
marketing services. Headquartered in Tulsa, OK, Rose Rock Midstream has
operations in six states with the majority of its assets strategically located
in or connected to the Cushing, Oklahoma crude oil marketing hub.

SemGroup^®, Rose Rock Midstream^®, SemGas^®, SemMaterials Mèxico^MR,
SemStream^® and White Cliffs Pipeline^® are registered trademarks of SemGroup
Corporation.

Forward-Looking Statements

Certain matters contained in this press release include "forward-looking
statements" within the meaning of Section 27A of the Securities Act and
Section 21E of the Securities Exchange Act of 1934, as amended. We make these
forward-looking statements in reliance on the safe harbor protections provided
under the Private Securities Litigation Reform Act of 1995.

All statements, other than statements of historical fact, included in this
press release may constitute forward-looking statements. Although we believe
that the expectations reflected in these forward-looking statements are
reasonable, we cannot assure you that these expectations will prove to be
correct. These forward-looking statements are subject to certain known and
unknown risks and uncertainties, as well as assumptions that could cause
actual results to differ materially from those reflected in these forward
looking statements. Factors that might cause actual results to differ are
discussed from time to time in each of our documents and reports filed with
the Securities and Exchange Commission.

Readers are cautioned not to place undue reliance on any forward-looking
statements contained in this press release, which reflect management's
opinions only as of the date hereof. Except as required by law, we undertake
no obligation to revise or publicly release the results of any revision to any
forward-looking statements.

CONTACT: Investor Relations:
         Mary Catherine Ward
         918-524-8081
         investor.relations@semgroupcorp.com
        
         Media:
         Kiley Roberson
         918-524-8594
         kroberson@semgroupcorp.com

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