"All 22 players made valuable team and individual contributions and as coaches, we take huge satisfaction from that," said Lewis.
"It was the best of the season so far".
The Drovers led by two tries to one at half-time with scores from wing Chris Knight and prop Dean Howells. Fly-half Andy Skeen replied for Melrose.
Soon after the restart Llandovery got their third try when a sweeping move sent wing Jake Randall racing in and this seemed to take the wind out of the Melrose sails.
Scrum half Rhodri Williams sealed the bonus point with try number four to make it 24-7 and although the Scots did get a second try courtesy of impressive flanker Roddy Grant, the Drovers finished the stronger.
No. 8 and man of the match Luke Kendall, lock Bryn Griffiths and flanker Shaun Miles were continually to the fore and North Walian Jack Roberts got a smart 77th minute try to cap another excellent display by the in-form Drovers.