Deputy Minister for Climate Change Lee Waters announced the new road building projects freeze, pending the outcome of the review.
Progress will be halted on a trio of schemes, including the £300m Deeside “Red Route”, the £50m Llandeilo bypass, and the £135m Third Menai Crossing.
Projects where work has started on the ground will not be impacted.
Ministers want to shift money from new roads to maintaining existing routes and investing in public transport.
Waters told the Senedd: “Since 1990, Welsh emissions have fallen by 31%.
“But to reach our statutory target of net zero emissions by 2050, we need to do much more.
“In the next 10 years, we are going to need to more than double all the cuts we have managed over the last 30 years, if we are going keep temperature rises within safe limits.”
He added: “That means changes in all parts of our lives. Transport makes up some 17% of our total emissions and so must play its part.
“We need a shift away from spending money on projects that encourage more people to drive and spend more money on maintaining our roads and investing in real alternatives that give people a meaningful choice.”
The full terms of reference for the review will be published in due course.
It is expected to consider how to shift spending towards better maintaining the existing roads, rather than building new ones, and look at all proposed road investments, whether funded directly by the Welsh Government or indirectly by grants.
The membership of the external panel that will carry out the review will be announced at a later date.
The panel will be asked to consider setting tests for when new roads are the right solutions for transport problems in line with Llwybr Newydd, the recently published Wales transport strategy.