Hansen, who guided New Zealand to a World Cup triumph in 2015 and is contracted until the end of next year's tournament in Japan, is expected to announce his long-term plans in the coming weeks.
Ireland coach Joe Schmidt was widely touted as a potential successor to Hansen but the New Zealander announced on Monday that he would quit coaching after the Japan World Cup to focus on his family.
Robertson, who guided the Crusaders to back-to-back Super Rugby titles in the last two years, is out of contract at the end of 2019 and seen as a strong candidate to replace Hansen, along with Wales coach Warren Gatland and All Blacks assistant Ian Foster.
"The All Blacks job doesn't come up too often. When it does, you have to have a real good look at it," Robertson, who has coached New Zealand's under-20 side, told local media on Tuesday.
"The decision from Steve (Hansen) will play a really big part of it.
"The biggest thing for me, that's served me well, is the patience side of it, and the ability to get your timing right.
"I've got a great job at the moment and I've got a big decision in the next three or four months -- what's going to happen in 2020, and I'll just see where the cards fall with other coaches and just see what opportunities there are."
Schmidt has transformed second-ranked Ireland into genuine World Cup contenders and a team without fear of the All Blacks, who they beat 16-9 in Dublin earlier this month.
However, former All Blacks loose forward Robertson sympathised with Schmidt's decision to bow out after Japan.
"He's a great coach, and obviously he's made a family decision," Robertson said.
"He might just need a year or two before he fills the tank again, but I know international rugby does take its toll.
"It's rare that you go out on your own terms, and he's gone out on his own terms this time. Good on him. It's a big call and he's done the right thing for him and his family."
(Reporting by Ian Ransom in Melbourne; Editing by John O'Brien)
