Former House speaker Paul Ryan, who last year joined the rush of high-profile individuals launching special-purpose acquisition companies, is going to work at the private-equity firm he teamed up with in that effort. Mr. Ryan will join Solamere Capital, a private-equity firm founded by Utah Sen. Mitt Romney’s son Taggart, as well as Eric Scheuermann and Spencer Zwick, as a partner. Solamere, a Boston firm with more than $1 billion in assets, seeks to invest in high-growth companies and help them expand and create jobs, he said. He was inclined to join the firm because it takes a conservative approach...