Especially because this is a headline, it could be a compressed use of the figurative term "steamrolled."
On April 25, Politico ran a similar headline: Ryan likely to get rolled on tax reform.
The content of the article begins:
Donald Trump is set to steamroll Paul Ryan on tax reform, the issue the speaker has devoted his political career to achieving. But don’t expect Ryan to relinquish his pet cause easily.
Unlike the Politico piece, the Washington Post uses the word "rolled" only in the headline, not in the content, so we can only speculate, but evidently using "rolled" as a condensed form of "steamrolled" has recent precedent.
In this sense, either to "roll" or to "steamroll" means to best an opponent or force them in a particular direction against their will. See definitions below.
The terms are sometimes used interchangeably in sports reporting as well. In this recent example, there is no mention of who is getting rolled, but the use of "roll" in the headline appears to be shorthand for "steamroll" based on the subheading:
Headline: "Bulldogs roll their way to Sulphur"
Subheading: "Behind their two LSU-Eunice signees, Ascension Catholic was able to dominate Catholic of Pointe Coupee from start to finish and steamroll to a 10-1 victory that pushed them through to the semifinals after falling in the quarterfinals for three straight seasons.
MacMillan offers this definition of steamroll:
To defeat or destroy an opponent completely.
OED also offers a figurative definition and example of "steamroll" in this context:
(b) fig.; (also) to force or drive in a given direction (cf. steam-roller v. 2).
1975 Times 21 July 1/8 The ruling party..will steamroll the endorsement through.
It is not uncommon in headline writing to colloquialize or abbreviate expressions to make a concise point, especially in a piece as informal as the Post article in question. My interpretation of the headline is that Trump got steamrolled by the Democrats.
