"I found the course pretty straightforward and didn?t experience too many problems," Rotich told reporters after the race in Dili, which he completed in a time of 2:34:57.
"The biggest challenge was the heat. It got very hot... The race was very well-organised and the Timorese people who supported the race around the course were fantastic," he added.
Augusto Ramos Soares and Zeferino Guterres Magalhaes, both Timorese, bagged second and third spots about a minute later.
The women's race saw Australian Lucie Hardiman taking top spot in a time of 3:03:32, followed by Timorese Juventina Napoleao about 10 minutes later.
"I?ll make sure that many people know about next year?s marathon, this race will only get bigger and better. I?ve raced in marathons around the world and this race was tremendous," Hardiman said.
National heroine Aguida Amaral emerged third in a time of 3:22:26. The 36-year-old former refugee is one of only a handful of Timorese athletes to ever make it to the Olympics, having run in Sydney in 2000 and Athens four years later.
The marathon was President Jose Ramos-Horta's latest sporting brainchild after last year's inaugural Tour de Timor cycle race and an international fishing competition.
It's all part of a plan to "build bridges through sports, to build peace in the country, to build fraternity between this country, our people and peoples around the world", he said.