No 8 Seb Nagle-Taylor crashed over and Alex Dolly kicked two penalties as the Titans took an 11-0 lead into the break.
Cambridge hit back to within one point with a converted try and penalty before Dolly eased Rotherham worries with another penalty.
However, the visitors ran away with the match and left Rotherham with nothing to show for their efforts with two more tries.
Huddersfield’s National Two (North) promotion push was boosted as they ran out 15-10 winners over Stourbridge at Lockwood Park.
Full-back Tom Hodson touched down and stand-off Chris Johnson kicked a penalty in the first half, and after the break flanker Lewis Bradley touched down and Johnson converted. Stourbridge hit back in the final 10 minutes with a converted try and penalty, but the hosts hung on.
Leaders Hull Ionians came back from a first-half deficit to stay top of the table with a 35-29 win at Sedgley Park.
Ionians were 24-14 down at the break despite tries from winger Sam Wilson and prop Ben Bell.
Wilson brought Ionians back into the game with two further tries but it was No 8 Ed Falkingham who sealed the game for the East Yorkshire outfit, touching down in the 64th minute.
Otley ran in four tries against Hinckley in a 29-14 victory.
Hooker Joe Graham scored the first of his two tries after just two minutes, and centre Stephen Nolson also scored to help the Yorkshire side to a 14-0 lead with just 20 minutes gone.
Hinckley pulled one back, but Otley went on to lead 29-7 with Graham’s second try and another from full-back Ben Magee.
Wharfedale could not make it four wins in a row after they lost to second-placed Chester 28-25.
They trailed 21-8 at half-time with only centre Rhys Lovegrove having touched down.
After the break, they hit back to lead 25-21 with hooker Dan Stockdale and scrum-half Philip Woodhead having tries converted by Jack Blakeney-Edwards, who also kicked a penalty.
However, a late converted try saw Chester take the win.
Sheffield Tigers were held to an 18-18 draw by Leicester Lions.
Hull secured an emphatic 56-10 win over Lymm in the North Premier league.
The visitors ran in eight tries in their demolition of struggling Lymm to remain top of the table.
Sandal went 19-0 down inside the first 15 minutes against Vale of Lune before they scored 50 unanswered points in a 50-24 win.
Winger Danny Grainger crossed the line twice in three minutes for Sandal, and added another in the 42nd minute to complete a hat-trick and help Sandal hit back. Four more second-half scores came via a penalty try, stand-off Gregory Wood, winger James Ellar and full-back Jack Townend as Sandal moved up to fourth in the table, leapfrogging Harrogate, who tasted defeat at the hands of Alnwick, 13-10.
Ilkley came unstuck at third-placed Blaydon, the Durham team winning 36-10.
Scarborough went top of North One East after beating bottom-side Consett 31-14.
The Yorkshire side crossed the line five times in the win which sees them overtake Huddersfield YMCA after they failed to take away the maximum haul of points from their 18-16 win at Pocklington.
York and Morpeth, meanwhile, drew 16-16.