The phrase "roam across" is correct and can be used in written English.
It means to wander or travel across a wide area. Example: The nomads would often roam across the desert in search of water and food.
But sharks roam across extremely large home ranges.
I'd let my eyes roam across the desert.
The Indian elephant and the Africa savannah elephant roam across vast expanses of land.
In "Ah Liberty!" (2008) children roam across a junk-strewn, vaguely postapocalyptic rural terrain.
These bulbs are all distasteful to deer, which roam across our farm in increasing numbers.
Even behind bars, Lecter managed to roam across our minds as if they were open prairies.
He values, above all, a sense of mobility the freedom to roam across the musical landscape.
The horses have a permit that lets them roam across the refuge in three fenced areas.
Black-clad Khorasan militants, their faces covered in balaclavas, roam across North Waziristan in jeeps with tinted windows.
From one gallery to the next, the sun and clouds move and animals roam across seasons of Ahae's static landscape.
Mr. Farrell, of Jane's Addiction and Porno for Pyros, doubles as DJ Peretz, whose sets roam across genres and borderlines.
