undefinedComcast Corp. chief executive Brian Roberts built a colossus, branching out from cable and broadband into entertainment with the acquisition of NBCUniversal a decade ago. Now, he has to prove the company is equipped to compete amid a dramatic industry shift to streaming.

Mr. Roberts is out to show Wall Street that Comcast’s marriage of content and distribution puts it in a strong position to fight on two different fronts of the streaming wars. He has greenlighted new spending and partnerships meant to answer concerns from some investors and analysts that the company has been too timid to be a major streaming contender.

Comcast is alone among the industry’s titans with its all-encompassing approach: AT&T Inc. recently unwound its own bet that content and distribution can thrive under one roof, with its deal to spin off its WarnerMedia division into a merger with Discovery Inc.

Comcast’s CEO is also wrestling with whether to build or buy to become a streaming powerhouse, people close to him said. Several big players, including ViacomCBS Inc., Walt Disney Co. and Amazon.com Inc., have struck mergers meant to supercharge their streaming efforts.

Mr. Roberts, 61 years old and known as an aggressive deal maker in his two decades atop Comcast, has told people close to him that he doesn’t feel a need to seek a merger. But he is scoping out options, and ideas on the table include a potential tie-up with ViacomCBS Inc. or an acquisition of Roku Inc., one of the people said.