Add RoBERTa to the model suite (#2279)
Summary:
https://huggingface.co/FacebookAI/xlm-roberta-base
Pull Request resolved: https://github.com/pytorch/benchmark/pull/2279
Reviewed By: aaronenyeshi
Differential Revision: D59490274
Pulled By: xuzhao9
fbshipit-source-id: 1720f09e04603fc07c1825c2fb2f9062cda50701
