Did a freeBMD search for deaths of John Roberts between 1861 and 1865 in Durham, Staffordshire and Worcestershire.
LOTS to wade through!
Deaths Jun 1861 (>99%)
Roberts John Dudley 6c 22
Roberts John Gateshead 10a 331
Roberts John Newport Sh. 6a 549
Roberts John Winchcomb 6a 249
Deaths Dec 1861 (>99%)
Roberts John Upton 6c 183
Deaths Mar 1862 (>99%)
ROBERTS John Dudley 6c 65
ROBERTS John Wolverhampton 6b
ROBERTS John Wolverhampton 6b 294
ROBERTS John Wolverhampton 6b 345
ROBERTS John Ashborne 7b 327
ROBERTS John Burton 6b 20[7_]
ROBERTS John Stow on W 6a 2[6_]0
Deaths Jun 1862 (>99%)
ROBERTS John Sunderland 10a 256
ROBERTS John Pershore 6c 207
ROBERTS John Stoke T 6b 98
ROBERTS John Wolverhampton 6b 310
ROBERTS John William Wolverhampton 6b 295
Deaths Sep 1862 (>99%)
Roberts John Stockton 10a 21
Roberts John W Bromwich 6b 341
Roberts John Wolverhampton 6b 214
Roberts John Stourbridge 6c 86
Deaths Dec 1862 (>99%)
ROBERTS John Dudley 6c 73
ROBERTS John Dudley 6c 58
Deaths Mar 1863 (>99%)
ROBERTS John Dudley 6c 6
ROBERTS John Dudley 6c 69
ROBERTS John Lichfield 6b 295
Deaths Jun 1863 (>99%)
ROBERTS John Stoke T 6b 93
ROBERTS John Worcester 6c 172
Deaths Sep 1863 (>99%)
ROBERTS John Wolverhampton 6b 305
ROBERTS John Stoke T 6b 98
ROBERTS John Newcastle L 6b 35
Deaths Dec 1863 (>99%)
ROBERTS John Bromsgrove 6c 250
ROBERTS John Wolverhampton 6b 316
ROBERTS John Bullock Wolverhampton 6b 304
ROBERTS John William Dudley 6c 19
Deaths Mar 1864 (>99%)
ROBERTS John Wolverhampton 6b 335
ROBERTS John Dudley 6c 68
ROBERTS John Shipston 6d 430
ROBERTS John Stoke T. 6b 157
Deaths Jun 1864 (>99%)
ROBERTS John Bromsgrove 6c 262
ROBERTS John Dudley 6c 33
Deaths Sep 1864 (>99%)
Roberts John Stoke T 6b 111
Roberts John Wolstanton 6b 54 Scan available - click to view
Roberts John Dudley 6c 46
Deaths Dec 1864 (>99%)
Roberts John W Bromwich 6b 462
Roberts John Tewkesbury 6a 288
Deaths Mar 1865 (>99%)
ROBERTS John Dudley 6c 87
ROBERTS John Solihull 6d 348
ROBERTS John Bromsgrove 15c 313
ROBERTS John Kidderminster 6c 186
ROBERTS John Worcester 6c 217
ROBERTS John Worcester 6c 217
ROBERTS John Edward Penkridge 6b 286
ROBERTS John William Wolverhampton 6b 345
ROBERTS John William Stratford upon Avon 6d 394
Deaths Jun 1865 (>99%)
Roberts John Wolverhampton 6b 262
Roberts John Wolverhampton 6b 30_
Deaths Sep 1865 (>99%)
Roberts John Solihull 6D 295
Roberts John Easington 10a 214
Deaths Dec 1865 (>99%)
Roberts John Wolverhampton 6b 324
Roberts John Walsall 6b 390
I think we can probably discount any with middle names as he didn't use one on his marriage cert or any of the censuses.
I'm leaning towards the death in Easington as Maria is living there in 1871, but that might be another coincidence, of course. It seems more likely that they moved there, he died, and then she stayed there than if he died in Worcs and then she moved. But who knows?
I'm going to see if I can find a death in mining records for that time, as he's listed as a coal miner in 1851 and 1861 (and a move to Durham would totally make sense for a miner).