Spatial multi-criteria decision analysis (MCDA) is increasingly being used to inform urban green infrastructure planning. We explore the use of modern cloud computing technologies (Google Earth Engine) to facilitate public access to spatial MCDA of ecosystem services from green infrastructure. Using the spatial prioritization of green roof retrofitting in Oslo, Norway, as a case study, we present a web application that is a generalizable tool for engaging stakeholders in spatial planning of ecosystem restoration and nature-based solutions. In our application, green roof designers, owners and operators identified the relative importance of a suite of potential ecosystem services (ES) gained from retrofitting of green roofs, conditional on preference profiles expected by users of different building functional types. The ES assessed included temperature regulation, stormwater runoff mitigation, habitat for biodiversity, aesthetic value, and noise reduction. In Oslo we found high spatial correlation in ES deficits, implying that even large differences in stakeholder preferences for individual ES will lead MCDA to identify common interests in the spatial targeting of green roofs. Nevertheless, we found the interactive spatial MCDA web application to have potential for improving planning process efficiency in engaging stakeholders. In more heterogenous urban landscapes, with lower spatial correlation of individual ES, spatial MCDA also has scope to improve the output efficiency of spatial targeting of nature-based solutions such as green roofs. Link to web application: https://nina.earthengine.app/view/green-roof-mcda.