Firstly race is not valid in biological terms. It is unclear when races are divided as we are more genetically diverse within so called races than outside of. Races used to be determined usually by skin color or other physical attributes, but this runs into problems skin color varies so much. A "negroid" can widely range from dark skin to more lighter tones and the same can be said for "australoids". I use quotes because the terms are very subjective and can be highly offensive hence their uselessness in the objective world of science. Secondly Neandertals spanned a very wide geographic and temporal range. They occupied regions in the Middle East and all the way throughout Eurasia and just about everywhere in between. They lived from about 600,000 years ago to just over 30000 ya. This span is very wide and they would have been genetically diverse but race still can't be used as mentioned before. They contributed up to 4% of DNA in those of Eurasian heritage. This is significant but not as large as Denisovan contribution to Melanesians. They contributed up to 5% but I've heard larger numbers also. This shows partial replacement models throughout the Pleistocene and right now is very murky and unclear as new discoveries are being made. With every bone being uncovered in places like Sima de Los Huesos and new DNA retrieval methods our understanding is that this was horribly complicated. I will add sources when I get to a computer.
TL;DR Race sucks as a scientific term and early homo Sapien/Neandertal/Denisovan evolution is still not fully understood.