DSXchange

Is there a way to automatically generate a schema file?

I have a job that exports a dataset to a sequential file using RCP.

If I could generate the schema file for this dataset, it would be possible to import the sequential file back in to a dataset by using the schema file to specify the column names.

You're out of luck. All you can do is to import the Sequential File definition.
RCP, after all, makes columns appear "by magic". You do not have control of metadata, and can perforce not undertake usage or lineage analyses.