The 36-year-old, who is the oldest No 1 in history, brushed aside Bulgarian Grigor Dimitrov 6-2, 6-2 in a one-sided final.
In the Open era, only American Jimmy Connors has won more titles than Roger with 109.
In a post match interview, Roger said “What a fantastic week,”. “The goal at the commencement of the week was to make it to the semi-finals. This is absolutely amazing, I’m really pleased.”
Federer, the record 20-time Grand Slam winner, will reclaim the number one ranking he last held in October 2012 when the new ATP rankings are published on Monday.
He has played two tournaments this year and won both — the other being January’s Australian Open.
He is three years older than American Andre Agassi was when previously holding the record for oldest No 1 back in 2003.
This was his third Rotterdam title following successes in 2005 and 2012 and he now stands 12-0 for the season.
The inspired Swiss star needed just 55 minutes to dispatch Dimitrov who looked to be under-cooked in the quickfire final.
Federer now stands a perfect 7-0 over the Bulgarian in their head-to-head series.
Two breaks per set were enough for Federer to lift the trophy.
Federer will now decide within the next few days whether or not to travel to Dubai for the ATP event starting a week from Monday.
Federer has a home and training base in the UAE and has won the hardcourt tournament seven times.
His effort in Rotterdam appeared to take little out of him physically, with his only loss of a set coming in the quarter-final against Robin Haase.