Rosiky's had the habit of looking interested, suggesting a contented disposition and a reflective quality that was gay rather than grave.
你的句子少了几个单词,原句是这样的:
Rosicky’s face had the habit of looking interested, — suggested a contented disposition and a reflective quality that was gay rather than grave.
Rosicky的脸会习惯性地表现出一副(对你)感兴趣的神情,给人感觉安详,这说明他是个随和的人而不是个严肃的人。
grave = serious, sad, sullen, melancholy
gay = happy, funny, light-hearted
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如果不明白look interested的含义,参看下图,右边,他的脸部表情